International Standard Electric Corp
InternatioActive Patents
0
Total Holdings
367
Patent Holdings
Filter in Explorer →| Patent No. | Title | Status | Filing Date | Grant Date | Claims | Actions |
|---|---|---|---|---|---|---|
| DE2805332A1 | PUSH BUTTON SWITCH | Expired / Lapsed | 1978-02-09 | — | 0 | Details |
| GB1526896A | Optical fibre delay line | Expired / Lapsed | 1977-05-26 | — | 0 | Details |
| DE2611868A1 | DEVICE FOR TRAIN POSITION INDICATION | Expired / Lapsed | 1976-03-20 | — | 0 | Details |
| GB1442883A | Telephone system with special kinds of telephone sets | Expired / Lapsed | 1974-10-03 | — | 0 | Details |
| GB1146559A | Bearing indication system for digital measurement of azimuth | Expired / Lapsed | 1967-12-20 | — | 0 | Details |
| GB1131210A | Improvements in and relating to integrated circuit logic ma… | Expired / Lapsed | 1967-09-14 | — | 0 | Details |
| GB1122924A | Circuit arrangement for a centrally controlled exchange, se… | Expired / Lapsed | 1966-09-08 | — | 0 | Details |
| US4279152A | Temperature responsive device | Expired / Lapsed | 1979-02-22 | 1981-07-21 | 10 | Details |
| US4185285A | Radar for the detection of fixed targets in clutter | Expired / Lapsed | 1978-04-17 | 1980-01-22 | 8 | Details |
| US4173412A | Strain measurement | Expired / Lapsed | 1977-06-29 | 1979-11-06 | 16 | Details |
| US4142774A | Flexible optical transducer | Expired / Lapsed | 1977-06-10 | 1979-03-06 | 11 | Details |
| US4038653A | Train position indicator | Expired / Lapsed | 1976-03-16 | 1977-07-26 | 7 | Details |
| US3937625A | Radio frequency preparation of pure glass | Expired / Lapsed | 1974-08-02 | 1976-02-10 | 5 | Details |
| US3933455A | Method for joining optical fibre bundles | Expired / Lapsed | 1974-05-17 | 1976-01-20 | 3 | Details |
| US3932843A | Real-time control arrangement for a simulation device | Expired / Lapsed | 1973-11-23 | 1976-01-13 | 10 | Details |
| US3891807A | Electronic switching module | Expired / Lapsed | 1973-05-09 | 1975-06-24 | 5 | Details |
| US3865999A | Automatic telecommunication switching system | Expired / Lapsed | 1973-02-26 | 1975-02-11 | 15 | Details |
| US3825932A | Waveguide antenna | Expired / Lapsed | 1973-05-16 | 1974-07-23 | 4 | Details |
| US3810178A | Range-controlled variable gain device for pulse radar recei… | Expired / Lapsed | 1972-11-29 | 1974-05-07 | 9 | Details |
| US3803511A | Gallium arsenide laser fiber coupling | Expired / Lapsed | 1972-10-18 | 1974-04-09 | 9 | Details |
| US3790769A | System for fault detection and location on data lines | Expired / Lapsed | 1972-11-21 | 1974-02-05 | 17 | Details |
| US3772651A | Lock-out circuit | Expired / Lapsed | 1972-06-21 | 1973-11-13 | 39 | Details |
| US3760297A | Laser to optical fiber coupling | Expired / Lapsed | 1972-01-20 | 1973-09-18 | 16 | Details |
| US3710027A | System of time-division multiplex transmission via communic… | Expired / Lapsed | 1970-10-27 | 1973-01-09 | 10 | Details |
| US3686662A | Circuit arrangement for the presentation of waveforms on vi… | Expired / Lapsed | 1970-11-12 | 1972-08-22 | 13 | Details |
| US3678497A | Character generation system having bold font capability | Expired / Lapsed | 1970-12-17 | 1972-07-18 | 19 | Details |
| US3657631A | Converter circuits | Expired / Lapsed | 1970-11-25 | 1972-04-18 | 3 | Details |
| US3652798A | Telecommunication system | Expired / Lapsed | 1970-06-08 | 1972-03-28 | 11 | Details |
| US3646575A | Coin-operated apparatus and signalling system | Expired / Lapsed | 1969-12-03 | 1972-02-29 | 4 | Details |
| US3626112A | Automatic mobile radiotelephone networks | Expired / Lapsed | 1968-04-03 | 1971-12-07 | 2 | Details |
| US3619478A | Electrical connecting element | Expired / Lapsed | 1970-03-18 | 1971-11-09 | 2 | Details |
| US3602900A | Synchronizing system for data processing equipment clocks | Expired / Lapsed | 1969-10-03 | 1971-08-31 | 12 | Details |
| US3601591A | Digital differential analyzer employing counters controled … | Expired / Lapsed | 1968-08-12 | 1971-08-24 | 7 | Details |
| US3600519A | Subscriber subset for pcm telephone system | Expired / Lapsed | 1969-05-21 | 1971-08-17 | 6 | Details |
| US3578917A | Security circuit for multi-exchange telecommunication netwo… | Expired / Lapsed | 1969-06-16 | 1971-05-18 | 6 | Details |
| US3569635A | A telecommunication system with means for detecting faults … | Expired / Lapsed | 1967-10-10 | 1971-03-09 | 12 | Details |
| US3568125A | Thermistor | Expired / Lapsed | 1968-10-14 | 1971-03-02 | 12 | Details |
| US3567865A | Cross point switching network in a telecommunication system | Expired / Lapsed | 1968-01-18 | 1971-03-02 | 18 | Details |
| US3562716A | Data processing system | Expired / Lapsed | 1968-01-17 | 1971-02-09 | 0 | Details |
| US3557315A | Automatic telecommunication switching system and informatio… | Expired / Lapsed | 1968-01-18 | 1971-01-19 | 40 | Details |
| US3553590A | Electronic goniometer | Expired / Lapsed | 1968-11-19 | 1971-01-05 | 0 | Details |
| US3553387A | Dialing apparatus | Expired / Lapsed | 1967-10-26 | 1971-01-05 | 3 | Details |
| US3530459A | Analog-to-digital multiplex coder | Expired / Lapsed | 1966-07-18 | 1970-09-22 | 0 | Details |
| US3525816A | Loop supervision circuitry | Expired / Lapsed | 1966-06-07 | 1970-08-25 | 0 | Details |
| US3518509A | Complementary field-effect transistors on common substrate … | Expired / Lapsed | 1967-05-04 | 1970-06-30 | 0 | Details |
| US3510591A | Control for an automatic reveille alarm device in telephone… | Expired / Lapsed | 1966-06-01 | 1970-05-05 | 0 | Details |
| US3495237A | Nonlinear decoder | Expired / Lapsed | 1966-09-23 | 1970-02-10 | 0 | Details |
| US3492445A | Switching installation supervision systems | Expired / Lapsed | 1965-12-20 | 1970-01-27 | 0 | Details |
| US3483898A | Retractor | Expired / Lapsed | 1966-06-08 | 1969-12-16 | 0 | Details |
| US3480948A | Non-linear coder | Expired / Lapsed | 1966-12-12 | 1969-11-25 | 2 | Details |
| US3474412A | Error detection and correction equipment | Expired / Lapsed | 1965-10-20 | 1969-10-21 | 0 | Details |
| US3454717A | Code generating keyboard apparatus | Expired / Lapsed | 1966-05-17 | 1969-07-08 | 0 | Details |
| US3453551A | Pulse sequence detector employing a shift register controll… | Expired / Lapsed | 1966-11-02 | 1969-07-01 | 2 | Details |
| US3440614A | Input linking device between analog functions and a numeric… | Expired / Lapsed | 1966-07-18 | 1969-04-22 | 0 | Details |
| US3440600A | Method for control supervision and protection of vehicles | Expired / Lapsed | 1966-05-05 | 1969-04-22 | 1 | Details |
| US3434008A | Solid state scanning system | Expired / Lapsed | 1966-09-29 | 1969-03-18 | 0 | Details |
| US3420988A | Digital counting equipments | Expired / Lapsed | 1965-05-17 | 1969-01-07 | 0 | Details |
| US3400228A | Method and circuit arrangement for central supervision of t… | Expired / Lapsed | 1965-06-07 | 1968-09-03 | 0 | Details |
| US3395389A | Apparatus to indicate faults of components in self-correcti… | Expired / Lapsed | 1963-08-06 | 1968-07-30 | 2 | Details |
| US3375449A | Frequency divider with variable digital ratio | Expired / Lapsed | 1965-05-12 | 1968-03-26 | 2 | Details |
| US3373424A | Tracking and synchronizing system | Expired / Lapsed | 1966-04-29 | 1968-03-12 | 0 | Details |
| US3366948A | Reference level zero adjuster for analog to digital convert… | Expired / Lapsed | 1964-07-09 | 1968-01-30 | 0 | Details |
| US3349399A | Beacon system for simultaneous azimuth and elevation determ… | Expired / Lapsed | 1966-02-23 | 1967-10-24 | 2 | Details |
| US3341848A | Method for the counting of vehicles the speed of which eith… | Expired / Lapsed | 1965-09-20 | 1967-09-12 | 2 | Details |
| US3339202A | Radiolocation system transmitting sideband signals | Expired / Lapsed | 1964-10-05 | 1967-08-29 | 1 | Details |
| US3336444A | Selective call system | Expired / Lapsed | 1964-03-11 | 1967-08-15 | 2 | Details |
| US3336443A | Pilot network selection systems | Expired / Lapsed | 1964-02-18 | 1967-08-15 | 2 | Details |
| US3324432A | Sealed contact makers including diaphragms for closing cont… | Expired / Lapsed | 1966-07-27 | 1967-06-06 | 2 | Details |
| US3304373A | Long distance tasi communication systems having answer-back… | Expired / Lapsed | 1963-03-13 | 1967-02-14 | 2 | Details |
| US3298024A | Method and device for distance measuring with the aid of el… | Expired / Lapsed | 1965-04-29 | 1967-01-10 | 2 | Details |
| US3281537A | Multiplex switching stage and its associated control circui… | Expired / Lapsed | 1962-10-11 | 1966-10-25 | 2 | Details |
| US3281536A | Pcm switching stage and its associated circuits | Expired / Lapsed | 1962-08-17 | 1966-10-25 | 2 | Details |
| US3274339A | Time division multiplex transmission systems | Expired / Lapsed | 1962-05-09 | 1966-09-20 | 2 | Details |
| US3234513A | Character recognition apparatus | Expired / Lapsed | 1961-08-10 | 1966-02-08 | 2 | Details |
| US3226486A | Selection system | Expired / Lapsed | 1962-03-05 | 1965-12-28 | 2 | Details |
| US3226482A | Selective transmission of priority coded message signals | Expired / Lapsed | 1961-09-21 | 1965-12-28 | 2 | Details |
| US3208047A | Data processing equipment | Expired / Lapsed | 1960-03-30 | 1965-09-21 | 2 | Details |
| US3205373A | Direct coupled semiconductor solid state circuit having com… | Expired / Lapsed | 1962-09-26 | 1965-09-07 | 2 | Details |
| US3200307A | Alternating current signal receiver | Expired / Lapsed | 1962-06-11 | 1965-08-10 | 2 | Details |
| US3181143A | Omni-directional altimetric radar | Expired / Lapsed | 1961-03-06 | 1965-04-27 | 2 | Details |
| US3181123A | Data processing systems | Expired / Lapsed | 1959-02-05 | 1965-04-27 | 2 | Details |
| US3181121A | Electronic programme-control | Expired / Lapsed | 1958-11-25 | 1965-04-27 | 2 | Details |
| US3174134A | Electric translator of the matrix type comprising a couplin… | Expired / Lapsed | 1962-01-17 | 1965-03-16 | 2 | Details |
| US3174135A | Program-controlled electronic data-processing system | Expired / Lapsed | 1959-02-25 | 1965-03-16 | 2 | Details |
| US3167166A | Printing arrangement for high-speed teleprinters | Expired / Lapsed | 1961-04-04 | 1965-01-26 | 2 | Details |
| US3133173A | Rotating magnetic reed switch | Expired / Lapsed | 1961-07-12 | 1964-05-12 | 2 | Details |
| US3131264A | Multi-frequency signalling receivers | Expired / Lapsed | 1961-04-05 | 1964-04-28 | 2 | Details |
| US3130387A | Buffer system for transferring data between two asynchronou… | Expired / Lapsed | 1959-02-05 | 1964-04-21 | 2 | Details |
| US3129302A | Switching device comprising reed contacts operated by perma… | Expired / Lapsed | 1962-03-29 | 1964-04-14 | 2 | Details |
| US3118131A | Data processing equipment | Expired / Lapsed | 1957-08-26 | 1964-01-14 | 2 | Details |
| US3078150A | Production of semi-conductor materials | Expired / Lapsed | 1959-05-01 | 1963-02-19 | 1 | Details |
| FR1307396A | Data operating system | Expired / Lapsed | 1961-09-22 | 1962-10-26 | 0 | Details |
| US3053993A | Magnetic trigger devices | Expired / Lapsed | 1959-09-17 | 1962-09-11 | 0 | Details |
| US3049593A | Switching systems between multiplex communication channels | Expired / Lapsed | 1959-10-19 | 1962-08-14 | 0 | Details |
| US3025522A | Doppler-type direction-finder | Expired / Lapsed | 1959-04-14 | 1962-03-13 | 0 | Details |
| US3025495A | Automatic character recognition | Expired / Lapsed | 1959-01-12 | 1962-03-13 | 0 | Details |
| US3024993A | Intelligence storage equipment | Expired / Lapsed | 1954-06-16 | 1962-03-13 | 0 | Details |
| US3013217A | Maser type oscillator | Expired / Lapsed | 1959-04-17 | 1961-12-12 | 0 | Details |
| US3013251A | Data processing equipment | Expired / Lapsed | 1957-11-08 | 1961-12-12 | 0 | Details |
| US3013120A | Data processing systems | Expired / Lapsed | 1957-10-08 | 1961-12-12 | 0 | Details |
| US3008019A | Reed-contact thermo relay | Expired / Lapsed | 1959-07-29 | 1961-11-07 | 0 | Details |
| US3001021A | Electrical information storage arrangements | Expired / Lapsed | 1954-03-18 | 1961-09-19 | 0 | Details |
| US2999227A | Circuit arrangement for the transmission of signal pulses a… | Expired / Lapsed | 1957-07-24 | 1961-09-05 | 0 | Details |
| US2991369A | Apparatus for determining the position of printed items | Expired / Lapsed | 1957-05-14 | 1961-07-04 | 0 | Details |
| US2985865A | Circuit arrangement for controlling a buffer storage | Expired / Lapsed | 1958-10-15 | 1961-05-23 | 0 | Details |
| US2980235A | Arrangement to produce electrical signals in belt conveyors… | Expired / Lapsed | 1957-08-01 | 1961-04-18 | 0 | Details |
| US2979244A | Record tape assembly and magazine therefor | Expired / Lapsed | 1956-12-13 | 1961-04-11 | 0 | Details |
| US2977574A | Electrical comparator | Expired / Lapsed | 1957-01-28 | 1961-03-28 | 0 | Details |
| US2974222A | Communication systems | Expired / Lapsed | 1958-03-28 | 1961-03-07 | 0 | Details |
| US2932695A | Automatic telephone systems | Expired / Lapsed | 1956-01-25 | 1960-04-12 | 0 | Details |
| US2928949A | Method of and apparatus for locating an identification mark… | Expired / Lapsed | 1957-07-05 | 1960-03-15 | 0 | Details |
| US2921267A | Protection against failure of pilot wave in carrier communi… | Expired / Lapsed | 1956-02-23 | 1960-01-12 | 0 | Details |
| US2911149A | Calculating means | Expired / Lapsed | 1956-08-08 | 1959-11-03 | 0 | Details |
| US2911475A | Electrical signalling systems | Expired / Lapsed | 1954-11-26 | 1959-11-03 | 0 | Details |
| US2906890A | Electrical circuits employing transistors | Expired / Lapsed | 1955-03-17 | 1959-09-29 | 0 | Details |
| US2901676A | Arrangement to produce electrical signals through affecting… | Expired / Lapsed | 1955-03-15 | 1959-08-25 | 0 | Details |
| US2886739A | Electronic distributor devices | Expired / Lapsed | 1952-10-20 | 1959-05-12 | 0 | Details |
| US2877718A | Arrangement for the destination-marking of dispatch contain… | Expired / Lapsed | 1955-04-04 | 1959-03-17 | 0 | Details |
| US2871464A | Methods of recording intelligence | Expired / Lapsed | 1954-03-22 | 1959-01-27 | 0 | Details |
| US2860324A | Power line signalling system | Expired / Lapsed | 1953-11-25 | 1958-11-11 | 0 | Details |
| US2857059A | Device for storing switching information for controlling op… | Expired / Lapsed | 1954-07-20 | 1958-10-21 | 0 | Details |
| US2850249A | Arrangements for selectively actuating control devices by m… | Expired / Lapsed | 1956-02-06 | 1958-09-02 | 0 | Details |
| US2847657A | Storage of electrical intelligence | Expired / Lapsed | 1954-05-19 | 1958-08-12 | 0 | Details |
| US2843765A | Circuit element having a negative resistance | Expired / Lapsed | 1953-03-09 | 1958-07-15 | 0 | Details |
| US2838745A | Methods of recording and/or modifying electrical intelligen… | Expired / Lapsed | 1952-05-22 | 1958-06-10 | 0 | Details |
| US2836878A | Electric devices employing semiconductors | Expired / Lapsed | 1953-04-20 | 1958-06-03 | 2 | Details |
| US2832899A | Electric trigger circuits | Expired / Lapsed | 1955-03-22 | 1958-04-29 | 0 | Details |
| US2831150A | Electrical information storage circuits | Expired / Lapsed | 1951-09-24 | 1958-04-15 | 0 | Details |
| US2828358A | Multiple telegraph signal regenerators | Expired / Lapsed | 1954-02-11 | 1958-03-25 | 0 | Details |
| US2825890A | Electrical information storage equipment | Expired / Lapsed | 1953-08-03 | 1958-03-04 | 0 | Details |
| US2822422A | Start-stop telegraph regenerators | Expired / Lapsed | 1954-08-16 | 1958-02-04 | 0 | Details |
| US2817817A | Measuring instrument | Expired / Lapsed | 1954-08-30 | 1957-12-24 | 0 | Details |
| US2815182A | Dispatch tube system | Expired / Lapsed | 1955-09-27 | 1957-12-03 | 0 | Details |
| US2814440A | Memory system | Expired / Lapsed | 1952-09-04 | 1957-11-26 | 0 | Details |
| US2812388A | Two way repeaters | Expired / Lapsed | 1954-08-30 | 1957-11-05 | 0 | Details |
| US2812134A | Binary electrical counting circuit | Expired / Lapsed | 1953-06-22 | 1957-11-05 | 0 | Details |
| US2807004A | Electrical intelligence storage arrangement | Expired / Lapsed | 1955-05-25 | 1957-09-17 | 0 | Details |
| US2799754A | Regulating device for electrical switching equipment | Expired / Lapsed | 1954-07-08 | 1957-07-16 | 0 | Details |
| US2784851A | Arrangement for use in conveying plants employing magnetic … | Expired / Lapsed | 1952-11-12 | 1957-03-12 | 0 | Details |
| US2784255A | Keyed frequency modulation carrier wave systems | Expired / Lapsed | 1951-11-29 | 1957-03-05 | 0 | Details |
| US2774534A | Electrical counting and like devices | Expired / Lapsed | 1952-07-10 | 1956-12-18 | 0 | Details |
| US2774747A | Electrically conducting cements containing epoxy resins and… | Expired / Lapsed | 1952-03-25 | 1956-12-18 | 0 | Details |
| US2773250A | Device for storing information | Expired / Lapsed | 1955-05-05 | 1956-12-04 | 0 | Details |
| US2770739A | Trigger circuits | Expired / Lapsed | 1954-02-15 | 1956-11-13 | 0 | Details |
| US2770676A | Automatic telephone systems | Expired / Lapsed | 1953-11-17 | 1956-11-13 | 0 | Details |
| US2770740A | Electric counting devices and circuits employing semi-condu… | Expired / Lapsed | 1952-10-10 | 1956-11-13 | 0 | Details |
| US2764754A | Electrical remote control and supervisory systems | Expired / Lapsed | 1951-07-21 | 1956-09-25 | 0 | Details |
| US2761351A | Indicating system for reading film | Expired / Lapsed | 1952-06-26 | 1956-09-04 | 0 | Details |
| US2761621A | Electric calculating circuits | Expired / Lapsed | 1950-11-24 | 1956-09-04 | 0 | Details |
| US2752523A | Electron discharge apparatus | Expired / Lapsed | 1952-04-08 | 1956-06-26 | 0 | Details |
| US2740076A | Crystal triodes | Expired / Lapsed | 1952-04-04 | 1956-03-27 | 2 | Details |
| US2723302A | Mounting plate insulators and assemblies | Expired / Lapsed | 1951-08-20 | 1955-11-08 | 0 | Details |
| US2723309A | Telephone system | Expired / Lapsed | 1950-03-10 | 1955-11-08 | 0 | Details |
| US2713132A | Electric rectifying devices employing semiconductors | Expired / Lapsed | 1953-10-07 | 1955-07-12 | 0 | Details |
| US2712623A | Anti-hunt circuit for electric motor follow-up system | Expired / Lapsed | 1952-06-19 | 1955-07-05 | 0 | Details |
| US2701216A | Method of making surface-type and point-type rectifiers and… | Expired / Lapsed | 1950-04-05 | 1955-02-01 | 2 | Details |
| US2694753A | System of identification of the calling line in telephone s… | Expired / Lapsed | 1950-12-29 | 1954-11-16 | 0 | Details |
| US2691743A | Horizontal line registration for pickup tubes | Expired / Lapsed | 1950-01-26 | 1954-10-12 | 0 | Details |
| US2688661A | Electronic switching | Expired / Lapsed | 1950-01-06 | 1954-09-07 | 0 | Details |
| US2680220A | Crystal diode and triode | Expired / Lapsed | 1951-05-26 | 1954-06-01 | 0 | Details |
| US2680159A | Amplifier employing semiconductors | Expired / Lapsed | 1951-03-13 | 1954-06-01 | 0 | Details |
| US2672589A | Electric frequency modulation system of communication | Expired / Lapsed | 1950-06-22 | 1954-03-16 | 0 | Details |
| US2668870A | Printing telegraph receiver | Expired / Lapsed | 1951-08-14 | 1954-02-09 | 0 | Details |
| US2667538A | Automatic telephone ticketing system | Expired / Lapsed | 1950-03-03 | 1954-01-26 | 0 | Details |
| US2663767A | Stabilized crystal triode system | Expired / Lapsed | 1951-05-23 | 1953-12-22 | 0 | Details |
| US2660618A | Signal translation system | Expired / Lapsed | 1948-01-20 | 1953-11-24 | 0 | Details |
| US2655605A | Alternating current switching device | Expired / Lapsed | 1951-11-15 | 1953-10-13 | 0 | Details |
| US2655607A | Electric delay device employing semiconductors | Expired / Lapsed | 1949-10-20 | 1953-10-13 | 0 | Details |
| US2653996A | Electric telegraph system | Expired / Lapsed | 1951-11-10 | 1953-09-29 | 0 | Details |
| US2653374A | Electric semiconductor | Expired / Lapsed | 1950-03-18 | 1953-09-29 | 0 | Details |
| US2654049A | Electron switch control system | Expired / Lapsed | 1947-04-30 | 1953-09-29 | 0 | Details |
| US2651716A | Pulse code modulation demodulator | Expired / Lapsed | 1948-10-23 | 1953-09-08 | 0 | Details |
| US2649505A | Pulse time position switching system | Expired / Lapsed | 1947-12-30 | 1953-08-18 | 0 | Details |
| US2648785A | Integral electrode with lead wire anchor for piezoelectric … | Expired / Lapsed | 1949-11-12 | 1953-08-11 | 0 | Details |
| US2645764A | Intelligence exchange system | Expired / Lapsed | 1950-06-14 | 1953-07-14 | 0 | Details |
| US2643353A | Traveling wave tube | Expired / Lapsed | 1948-11-04 | 1953-06-23 | 0 | Details |
| US2642558A | Electric power supply equipment | Expired / Lapsed | 1949-05-26 | 1953-06-16 | 0 | Details |
| US2641730A | Velocity modulation amplifier tube | Expired / Lapsed | 1947-10-07 | 1953-06-09 | 0 | Details |
| US2641701A | Timing device | Expired / Lapsed | 1947-08-30 | 1953-06-09 | 0 | Details |
| US2640951A | Microwave amplifier of the magnetron type | Expired / Lapsed | 1949-06-25 | 1953-06-02 | 0 | Details |
| US2640501A | Tube and its manufacture | Expired / Lapsed | 1948-02-27 | 1953-06-02 | 0 | Details |
| US2640881A | Multichannel electrical pulse communication system | Expired / Lapsed | 1947-07-03 | 1953-06-02 | 0 | Details |
| US2638505A | Pulse electronic switching system | Expired / Lapsed | 1948-03-24 | 1953-05-12 | 0 | Details |
| US2629776A | Telegraph receiver | Expired / Lapsed | 1952-03-14 | 1953-02-24 | 0 | Details |
| US2629857A | Communication system utilizing constant amplitude pulses of… | Expired / Lapsed | 1947-10-08 | 1953-02-24 | 0 | Details |
| US2629829A | Method of calibrating electric oscillation generators | Expired / Lapsed | 1946-10-22 | 1953-02-24 | 0 | Details |
| US2626996A | Conversion from direct current to double voice frequency im… | Expired / Lapsed | 1948-02-04 | 1953-01-27 | 0 | Details |
| US2626987A | Automatic switching system for electrical telecommunications | Expired / Lapsed | 1947-07-03 | 1953-01-27 | 0 | Details |
| US2626993A | Control of carrier transmission systems by pilot frequencies | Expired / Lapsed | 1947-06-07 | 1953-01-27 | 0 | Details |
| US2619548A | Electronic switching apparatus for telephone systems | Expired / Lapsed | 1948-05-15 | 1952-11-25 | 0 | Details |
| US2617752A | Method for dielectric r-f heating of nonconducting material… | Expired / Lapsed | 1950-11-25 | 1952-11-11 | 2 | Details |
| US2607903A | Distributor tube construction | Expired / Lapsed | 1947-11-10 | 1952-08-19 | 0 | Details |
| US2607528A | Electrical measuring circuits | Expired / Lapsed | 1947-01-02 | 1952-08-19 | 0 | Details |
| US2601281A | Binary add-subtract device | Expired / Lapsed | 1943-07-12 | 1952-06-24 | 0 | Details |
| US2597043A | Automatic replacement of defective repeaters in high-freque… | Expired / Lapsed | 1949-07-12 | 1952-05-20 | 0 | Details |
| US2597029A | Superheterodyne radio receiver employing a multifunction tu… | Expired / Lapsed | 1946-09-21 | 1952-05-20 | 0 | Details |
| US2588923A | Calculator | Expired / Lapsed | 1946-01-16 | 1952-03-11 | 0 | Details |
| US2586810A | Localizer and glide path system | Expired / Lapsed | 1947-10-21 | 1952-02-26 | 0 | Details |
| US2577755A | Alternating-current signaling system | Expired / Lapsed | 1948-04-27 | 1951-12-11 | 0 | Details |
| US2576099A | Electrical translator of finary code to decimal code | Expired / Lapsed | 1947-10-29 | 1951-11-27 | 0 | Details |
| US2572074A | Voice-frequency signaling system | Expired / Lapsed | 1948-07-07 | 1951-10-23 | 0 | Details |
| US2570279A | Electric signaling system | Expired / Lapsed | 1949-04-06 | 1951-10-09 | 0 | Details |
| US2570220A | Pulse code modulation system | Expired / Lapsed | 1949-02-10 | 1951-10-09 | 0 | Details |
| US2570221A | Pulse code modulation system | Expired / Lapsed | 1949-02-10 | 1951-10-09 | 0 | Details |
| US2570274A | Electron beam switching tube and system | Expired / Lapsed | 1946-03-14 | 1951-10-09 | 0 | Details |
| US2568724A | Electric pulse code modulation system of communication | Expired / Lapsed | 1949-02-10 | 1951-09-25 | 0 | Details |
| US2567226A | Electric remote-control system | Expired / Lapsed | 1947-08-07 | 1951-09-11 | 0 | Details |
| US2565497A | Circuit, including negative resistance device | Expired / Lapsed | 1949-07-21 | 1951-08-28 | 0 | Details |
| US2565486A | Pulse duration separation system | Expired / Lapsed | 1947-11-10 | 1951-08-28 | 0 | Details |
| US2561051A | Group selection control circuit | Expired / Lapsed | 1950-06-12 | 1951-07-17 | 0 | Details |
| US2556200A | Electrical translation system | Expired / Lapsed | 1948-02-26 | 1951-06-12 | 0 | Details |
| US2556242A | Automatic equalizer | Expired / Lapsed | 1947-03-08 | 1951-06-12 | 0 | Details |
| US2553585A | Electric discharge tube | Expired / Lapsed | 1949-09-27 | 1951-05-22 | 0 | Details |
| US2551619A | Electric time constant circuit | Expired / Lapsed | 1947-08-19 | 1951-05-08 | 0 | Details |
| US2551591A | Polyethylene bonded to copper by means of a layer of cuprou… | Expired / Lapsed | 1945-10-22 | 1951-05-08 | 1 | Details |
| US2549769A | Arrangement for counting electrical impulses | Expired / Lapsed | 1944-11-02 | 1951-04-24 | 0 | Details |
| US2547011A | Electric fault alarm circuits | Expired / Lapsed | 1947-05-14 | 1951-04-03 | 0 | Details |
| US2546984A | Communication system | Expired / Lapsed | 1947-04-02 | 1951-04-03 | 0 | Details |
| US2547035A | Electric signaling system | Expired / Lapsed | 1947-01-02 | 1951-04-03 | 0 | Details |
| US2546973A | Arrangement for determining distance by means of electromag… | Expired / Lapsed | 1942-12-10 | 1951-04-03 | 0 | Details |
| US2543053A | Radiant energy high-temperature heating apparatus | Expired / Lapsed | 1947-12-01 | 1951-02-27 | 0 | Details |
| US2541055A | Radio telegraph transmitter | Expired / Lapsed | 1947-06-19 | 1951-02-13 | 0 | Details |
| US2538035A | Absorbing screen for directive radiation | Expired / Lapsed | 1948-04-03 | 1951-01-16 | 0 | Details |
| US2527512A | Multiplex counting system | Expired / Lapsed | 1947-08-14 | 1950-10-31 | 0 | Details |
| US2527547A | Self-contained radio guiding apparatus for mobile craft | Expired / Lapsed | 1943-05-15 | 1950-10-31 | 0 | Details |
| US2524861A | Telemetering system for radio links | Expired / Lapsed | 1947-12-11 | 1950-10-10 | 0 | Details |
| US2520125A | Pulse code system | Expired / Lapsed | 1948-03-16 | 1950-08-29 | 0 | Details |
| US2516915A | Gaseous discharge device | Expired / Lapsed | 1947-10-03 | 1950-08-01 | 0 | Details |
| US2512639A | Control or signaling system | Expired / Lapsed | 1947-10-07 | 1950-06-27 | 0 | Details |
| US2512680A | Electronic pulse transmission system | Expired / Lapsed | 1947-10-03 | 1950-06-27 | 0 | Details |
| US2512613A | Selective call system | Expired / Lapsed | 1947-07-25 | 1950-06-27 | 0 | Details |
| US2512658A | Amplitude control of electric oscillations | Expired / Lapsed | 1943-02-27 | 1950-06-27 | 0 | Details |
| US2510054A | Pulse code communication system | Expired / Lapsed | 1948-01-20 | 1950-06-06 | 0 | Details |
| US2510062A | Electronic signal regenerator for translating alternating c… | Expired / Lapsed | 1945-01-29 | 1950-06-06 | 0 | Details |
| US2505006A | Gaseous discharge device | Expired / Lapsed | 1947-10-03 | 1950-04-25 | 0 | Details |
| US2504999A | Electric signaling system | Expired / Lapsed | 1947-04-25 | 1950-04-25 | 0 | Details |
| US2502415A | Line finder allotter circuit for telephone exchanges | Expired / Lapsed | 1944-06-23 | 1950-04-04 | 0 | Details |
| US2498695A | Telegraph receiver | Expired / Lapsed | 1947-04-25 | 1950-02-28 | 0 | Details |
| US2495752A | Arrangement for measuring electric power | Expired / Lapsed | 1945-06-30 | 1950-01-31 | 0 | Details |
| US2490039A | Arrangement for selection and demodulation of electrical pu… | Expired / Lapsed | 1945-01-16 | 1949-12-06 | 0 | Details |
| US2489325A | Electrical storage of information | Expired / Lapsed | 1947-10-25 | 1949-11-29 | 0 | Details |
| US2489313A | Frequency modulation discriminator | Expired / Lapsed | 1947-03-08 | 1949-11-29 | 0 | Details |
| US2489302A | Multichannel time modulated electrical pulse communication … | Expired / Lapsed | 1945-07-02 | 1949-11-29 | 0 | Details |
| US2485652A | Regulated radio frequency power supply | Expired / Lapsed | 1947-11-10 | 1949-10-25 | 0 | Details |
| US2485556A | Facsimile communication system | Expired / Lapsed | 1943-05-15 | 1949-10-25 | 0 | Details |
| US2482820A | Periodic electromagnetic relay | Expired / Lapsed | 1943-04-17 | 1949-09-27 | 0 | Details |
| US2476985A | Receiver for electrical pulses | Expired / Lapsed | 1945-01-16 | 1949-07-26 | 0 | Details |
| US2474253A | Means for measuring difference in frequency of alternating … | Expired / Lapsed | 1944-02-24 | 1949-06-28 | 0 | Details |
| US2471457A | Time and thermostatically controlled switching arrangement | Expired / Lapsed | 1944-07-17 | 1949-05-31 | 0 | Details |
| US2468082A | Thermistor circuit compensating for supply voltage fluctuat… | Expired / Lapsed | 1943-08-16 | 1949-04-26 | 0 | Details |
| US2468032A | Direction and distance indicating system | Expired / Lapsed | 1941-02-28 | 1949-04-26 | 0 | Details |
| CA455025A | Manufacture of insulated electric wire and cable | Expired / Lapsed | — | 1949-03-08 | 0 | Details |
| US2462111A | Multichannel pulse distributor system | Expired / Lapsed | 1945-07-02 | 1949-02-22 | 0 | Details |
| US2459846A | Voltage control arrangement | Expired / Lapsed | 1943-05-25 | 1949-01-25 | 0 | Details |
| US2457149A | Selective signaling circuit | Expired / Lapsed | 1947-03-20 | 1948-12-28 | 0 | Details |
| US2457136A | Arrangement for frequency measurements | Expired / Lapsed | 1945-01-16 | 1948-12-28 | 0 | Details |
| US2457125A | Circuit arrangement for producing electrical pulses | Expired / Lapsed | 1943-03-23 | 1948-12-28 | 0 | Details |
| US2454781A | Matched potential control system | Expired / Lapsed | 1945-09-17 | 1948-11-30 | 0 | Details |
| US2454780A | Telecommunication switching system | Expired / Lapsed | 1943-08-28 | 1948-11-30 | 0 | Details |
| US2454809A | Telephone system utilizing register controlled final select… | Expired / Lapsed | 1943-01-16 | 1948-11-30 | 0 | Details |
| US2452540A | Electrical condenser | Expired / Lapsed | 1947-02-07 | 1948-11-02 | 0 | Details |
| FR939015A | Rectifiers | Expired / Lapsed | 1946-03-23 | 1948-11-02 | 0 | Details |
| US2449985A | Receiver for pulse waves | Expired / Lapsed | 1941-10-30 | 1948-09-28 | 0 | Details |
| US2449976A | Tridimensional obstacle detection system | Expired / Lapsed | 1941-02-24 | 1948-09-28 | 0 | Details |
| US2444066A | Tuner for cavity resonators | Expired / Lapsed | 1943-06-03 | 1948-06-29 | 0 | Details |
| US2440250A | Radio location system | Expired / Lapsed | 1943-06-03 | 1948-04-27 | 0 | Details |
| US2436847A | Cathode-ray tube and visual indicating system for apparatus… | Expired / Lapsed | 1943-07-29 | 1948-03-02 | 0 | Details |
| US2434929A | Radio receiver circuits | Expired / Lapsed | 1944-01-12 | 1948-01-27 | 0 | Details |
| US2434919A | Method of braking asynchronous motors | Expired / Lapsed | 1941-10-30 | 1948-01-27 | 0 | Details |
| US2433407A | System of modulation transmission by means of impulses | Expired / Lapsed | 1943-07-02 | 1947-12-30 | 0 | Details |
| US2433384A | Method of manufacturing unitary multiple connections | Expired / Lapsed | 1942-11-05 | 1947-12-30 | 0 | Details |
| US2431344A | Determining distance by electromagnetic waves | Expired / Lapsed | 1944-02-22 | 1947-11-25 | 0 | Details |
| US2431333A | Electric wave amplifier | Expired / Lapsed | 1943-05-31 | 1947-11-25 | 0 | Details |
| US2431306A | Thermionic amplifier | Expired / Lapsed | 1943-05-08 | 1947-11-25 | 0 | Details |
| US2429608A | Multichannel pulse communication system | Expired / Lapsed | 1943-02-16 | 1947-10-28 | 0 | Details |
| US2429607A | Radio traffic signaling system | Expired / Lapsed | 1940-03-14 | 1947-10-28 | 0 | Details |
| US2428016A | Key-sender for telecommunication systems | Expired / Lapsed | 1945-05-14 | 1947-09-30 | 0 | Details |
| US2426218A | Instrument navigation system | Expired / Lapsed | 1942-03-23 | 1947-08-26 | 0 | Details |
| US2423103A | System for measuring frequency deviations | Expired / Lapsed | 1943-06-22 | 1947-07-01 | 0 | Details |
| US2423104A | Direction indicating apparatus | Expired / Lapsed | 1941-03-13 | 1947-07-01 | 0 | Details |
| US2421333A | Multiplex carrier current communication system with transmi… | Expired / Lapsed | 1943-04-13 | 1947-05-27 | 0 | Details |
| US2412994A | Radio receiving system | Expired / Lapsed | 1943-10-04 | 1946-12-24 | 0 | Details |
| US2412974A | Electric wave communication system | Expired / Lapsed | 1943-09-11 | 1946-12-24 | 0 | Details |
| US2410050A | Telecommunication switching system | Expired / Lapsed | 1944-04-21 | 1946-10-29 | 0 | Details |
| US2408037A | Electrical remote indicating and supervisory system | Expired / Lapsed | 1943-03-10 | 1946-09-24 | 0 | Details |
| US2408039A | Electronic rotation direction finder | Expired / Lapsed | 1941-03-05 | 1946-09-24 | 0 | Details |
| US2406800A | Direction finder with filter | Expired / Lapsed | 1941-03-13 | 1946-09-03 | 0 | Details |
| US2403967A | Radio direction finder | Expired / Lapsed | 1941-02-27 | 1946-07-16 | 0 | Details |
| US2381847A | System of communication by means of electrical waves | Expired / Lapsed | 1941-11-08 | 1945-08-07 | 0 | Details |
| US2374817A | Pulse generator, particularly for electric phase metering | Expired / Lapsed | 1943-05-24 | 1945-05-01 | 0 | Details |
| US2374810A | Electron discharge apparatus | Expired / Lapsed | 1940-11-27 | 1945-05-01 | 0 | Details |
| US2372593A | Telemetering system | Expired / Lapsed | 1942-11-24 | 1945-03-27 | 0 | Details |
| US2372620A | Blind landing system using electromagnetic waves | Expired / Lapsed | 1942-04-09 | 1945-03-27 | 0 | Details |
| US2372213A | Ultra-high-frequency tube | Expired / Lapsed | 1940-05-11 | 1945-03-27 | 0 | Details |
| US2369589A | Radio frequency circuits | Expired / Lapsed | 1942-11-24 | 1945-02-13 | 0 | Details |
| US2363941A | Angle indicating apparatus | Expired / Lapsed | 1941-03-05 | 1944-11-28 | 0 | Details |
| US2362209A | Ultra-high-frequency receiver | Expired / Lapsed | 1940-07-13 | 1944-11-07 | 0 | Details |
| US2357398A | Transmitter having impulse modulation | Expired / Lapsed | 1941-12-19 | 1944-09-05 | 0 | Details |
| US2354682A | Electric selection controlling circuit | Expired / Lapsed | 1943-05-06 | 1944-08-01 | 0 | Details |
| US2354510A | Automatic frequency control | Expired / Lapsed | 1942-07-17 | 1944-07-25 | 0 | Details |
| US2344885A | Electrical calculating equipment | Expired / Lapsed | 1939-11-09 | 1944-03-21 | 0 | Details |
| US2343759A | Electric signaling system | Expired / Lapsed | 1942-06-17 | 1944-03-07 | 0 | Details |
| US2338242A | Line identification | Expired / Lapsed | 1942-04-18 | 1944-01-04 | 0 | Details |
| US2336488A | Metal seal member | Expired / Lapsed | 1942-01-31 | 1943-12-14 | 0 | Details |
| US2334247A | Detected signal direction finder | Expired / Lapsed | 1941-03-06 | 1943-11-16 | 0 | Details |
| US2333322A | Apparatus for measuring phase differences and for analogous… | Expired / Lapsed | 1941-10-30 | 1943-11-02 | 0 | Details |
| US2328944A | Transmission system employing pulse modulation | Expired / Lapsed | 1940-05-08 | 1943-09-07 | 0 | Details |
| US2323560A | Electron discharge apparatus | Expired / Lapsed | 1940-12-11 | 1943-07-06 | 0 | Details |
| US2320908A | Radio compass | Expired / Lapsed | 1941-03-05 | 1943-06-01 | 0 | Details |
| US2320860A | Electron discharge apparatus | Expired / Lapsed | 1940-11-27 | 1943-06-01 | 0 | Details |
| US2317140A | Electron discharge apparatus | Expired / Lapsed | 1941-12-16 | 1943-04-20 | 0 | Details |
| US2316267A | Sleeve connector | Expired / Lapsed | 1942-03-23 | 1943-04-13 | 0 | Details |
| US2316238A | Telecommunication system | Expired / Lapsed | 1938-12-20 | 1943-04-13 | 0 | Details |
| US2313601A | Voltage divider | Expired / Lapsed | 1942-04-09 | 1943-03-09 | 0 | Details |
| US2312919A | Modulation system for velocity modulation tubes | Expired / Lapsed | 1940-09-19 | 1943-03-02 | 0 | Details |
| US2311574A | Battery charging equipment | Expired / Lapsed | 1941-11-08 | 1943-02-16 | 0 | Details |
| US2309966A | Velocity modulated electrical discharge tube | Expired / Lapsed | 1940-07-13 | 1943-02-02 | 0 | Details |
| US2308639A | Signaling and communication system | Expired / Lapsed | 1940-08-22 | 1943-01-19 | 0 | Details |
| US2306875A | Electron discharge apparatus | Expired / Lapsed | 1940-12-11 | 1942-12-29 | 0 | Details |
| US2304210A | Insulated electric cable | Expired / Lapsed | 1940-02-28 | 1942-12-08 | 0 | Details |
| US2304186A | Velocity modulated tube | Expired / Lapsed | 1939-12-14 | 1942-12-08 | 0 | Details |
| US2301251A | Tire inspection apparatus | Expired / Lapsed | 1939-12-13 | 1942-11-10 | 0 | Details |
| US2300394A | Pulse modulation system | Expired / Lapsed | 1940-08-22 | 1942-11-03 | 0 | Details |
| US2300613A | Street traffic control system | Expired / Lapsed | 1939-05-31 | 1942-11-03 | 0 | Details |
| US2298949A | Radial form ultra-high frequency tube | Expired / Lapsed | 1940-04-20 | 1942-10-13 | 0 | Details |
| US2298922A | Electric signaling system | Expired / Lapsed | 1940-01-06 | 1942-10-13 | 0 | Details |
| US2298939A | Train describer and platform indicator | Expired / Lapsed | 1939-06-09 | 1942-10-13 | 0 | Details |
| US2295025A | Electric signal-responsive device | Expired / Lapsed | 1940-03-15 | 1942-09-08 | 0 | Details |
| US2289745A | Metering equipment for telecommunication exchange systems | Expired / Lapsed | 1939-03-21 | 1942-07-14 | 0 | Details |
| US2287164A | Electric signaling system | Expired / Lapsed | 1937-06-04 | 1942-06-23 | 0 | Details |
| US2283999A | Calculating equipment | Expired / Lapsed | 1939-10-27 | 1942-05-26 | 0 | Details |
| US2282002A | Method of incorporating polymerized aliphatic mono-olefins … | Expired / Lapsed | 1938-11-03 | 1942-05-05 | 0 | Details |
| US2279762A | Electrical insulating material | Expired / Lapsed | 1938-12-20 | 1942-04-14 | 0 | Details |
| US2279713A | Telephone subset | Expired / Lapsed | 1938-10-29 | 1942-04-14 | 0 | Details |
| US2272607A | Navigation system and apparatus | Expired / Lapsed | 1939-11-02 | 1942-02-10 | 0 | Details |
| US2272070A | Electric signaling system | Expired / Lapsed | 1939-11-22 | 1942-02-03 | 0 | Details |
| US2266410A | Automatic radio-guiding system for vehicles | Expired / Lapsed | 1939-03-11 | 1941-12-16 | 0 | Details |
| US2266449A | Navigation apparatus | Expired / Lapsed | 1938-06-22 | 1941-12-16 | 0 | Details |
| US2262838A | Electric signaling system | Expired / Lapsed | 1938-11-08 | 1941-11-18 | 0 | Details |
| US2263377A | System for indicating the direction of propagation of elect… | Expired / Lapsed | 1938-10-08 | 1941-11-18 | 0 | Details |
| US2256336A | Pulse modulation system | Expired / Lapsed | 1940-01-09 | 1941-09-16 | 0 | Details |
| US2256300A | Device applicable mainly to television | Expired / Lapsed | 1937-10-15 | 1941-09-16 | 0 | Details |
| US2251984A | Oscillograph scale system | Expired / Lapsed | 1938-05-21 | 1941-08-12 | 0 | Details |
| US2251973A | Circuits for integrating and differentiating electric varia… | Expired / Lapsed | 1936-03-20 | 1941-08-12 | 0 | Details |
| US2248793A | Method of regulating the amplitude of electric waves | Expired / Lapsed | 1939-05-11 | 1941-07-08 | 0 | Details |
| US2238223A | Automatic hunting circuit | Expired / Lapsed | 1938-08-18 | 1941-04-15 | 0 | Details |
| US2238234A | Pressure indicator | Expired / Lapsed | 1937-09-23 | 1941-04-15 | 0 | Details |
| US2236134A | System of transmission of electric signals | Expired / Lapsed | 1939-01-07 | 1941-03-25 | 0 | Details |
| US2232076A | Electrical circuits for integrating electrical variations | Expired / Lapsed | 1938-04-06 | 1941-02-18 | 0 | Details |
| US2226728A | Transmission device | Expired / Lapsed | 1939-04-01 | 1940-12-31 | 0 | Details |
| US2223082A | High frequency transmission system | Expired / Lapsed | 1937-05-13 | 1940-11-26 | 0 | Details |
| US2219729A | Device employed in the conversion of electrical energy into… | Expired / Lapsed | 1937-06-17 | 1940-10-29 | 0 | Details |
| US2215776A | Time base circuit for cathode ray tubes | Expired / Lapsed | 1937-02-19 | 1940-09-24 | 0 | Details |
| US2214924A | Railway signaling system | Expired / Lapsed | 1938-05-28 | 1940-09-17 | 0 | Details |
| US2213273A | Radio direction finding apparatus | Expired / Lapsed | 1937-10-15 | 1940-09-03 | 0 | Details |
| US2212240A | Carrier wave modulating system and apparatus | Expired / Lapsed | 1937-04-16 | 1940-08-20 | 0 | Details |
| US2210651A | Radio beacon system | Expired / Lapsed | 1937-04-03 | 1940-08-06 | 0 | Details |
| US2209847A | Secondary emission device | Expired / Lapsed | 1937-10-20 | 1940-07-30 | 0 | Details |
| US2191993A | Telephone hand-set with combined transmitter and dial | Expired / Lapsed | 1937-04-28 | 1940-02-27 | 0 | Details |
| US2189925A | Gain control arrangement | Expired / Lapsed | 1936-04-29 | 1940-02-13 | 0 | Details |
| US2167529A | Apparatus for timing x-ray exposures | Expired / Lapsed | 1937-08-12 | 1939-07-25 | 0 | Details |
| US2164956A | Automatic stock quotation board | Expired / Lapsed | 1930-09-10 | 1939-07-04 | 0 | Details |
| US2147824A | Electrical insulating material | Expired / Lapsed | 1936-01-11 | 1939-02-21 | 0 | Details |
| US2134118A | Stock quotation monitoring and automatic shelf selection sy… | Expired / Lapsed | 1930-12-31 | 1938-10-25 | 0 | Details |
| US2108117A | Signaling system | Expired / Lapsed | 1936-01-24 | 1938-02-15 | 0 | Details |
| US2096170A | Light-sensitive device | Expired / Lapsed | 1934-03-31 | 1937-10-19 | 0 | Details |
| US1851482A | Automatic or semiautomatic telephone system | Expired / Lapsed | 1930-01-31 | 1932-03-29 | 0 | Details |