Patent US1486448A successfully refreshed from Google Patents.
Patent US1324740A successfully refreshed from Google Patents.
Patent US3697704A successfully refreshed from Google Patents.
US3697704A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Circuits for private automatic telephone exchange systems
Assignee: The General Electric Company PLC
•
Filing: 1970-10-01
•
Granted: 1972-10-10
•
Expires: 1990-10-01
Abstract
Abstract A detector circuit for use in a private exchange using pushbutton controlled ''''leg-signalling,'''' the circuit comprising four transistors different ones or combinations of which become conducting in response to currents resulting from the application of an alternating voltage to different combinations of terminations applied to the line wires by operation of respective pushbuttons at the extension. The combinations of terminations serve to indicate the digit values of the respective pushbuttons for the purpose of signalling to the exchange equipment the number of an extension to be called.
Inventors
- 👤 Michael Lawrence Jacobs
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 07:09
CPC Classifications
H; H04; H04Q; H04Q3/00; H04Q3/42
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
163 words
In a private automatic telephone exchange system in which subscriber-operated pushbuttons are used to apply combinations of a plurality of different terminations to the two line wires of the respective subscriber''s line in order to signal to the exchange the digits of a number to be called: the combination in the exchange of A. a detector circuit comprising i. two groups of transistors, ii. means to apply an alternating voltage to each of a respective subscriber''s line wires by way of an input circuit of each transistor of a respective one of said groups, iii. whereby different current flow conditions are developed in said input circuits in response to the application of different terminations to a respective subscriber''s line wires, and different ones or combinations of the transistors of a group are caused to conduct in response to the application of said different terminations, and B. means responsive to current flow through said transistors to register the value of a digit being signalled.
Claim 2
Dependent Claim
163 words
In a private automatic telephone exchange system in which subscriber-operated pushbuttons are used to apply combinations of a plurality of different terminations to the two line wires of the respective subscriber''s line in order to signal to the exchange the digits of a number to be called: the combination in the exchange of A. a detector circuit comprising i. two groups of transistors, ii. means to apply an alternating voltage to each of a respective subscriber''s line wires by way of an input circuit of each transistor of a respective one of said groups, iii. whereby different current flow conditions are developed in said input circuits in response to the application of different terminations to a respective subscriber''s line wires, and different ones or combinations of the transistors of a group are caused to conduct in response to the application of said different terminations, and B. means responsive to current flow through said transistors to register the value of a digit being signalled.
Claim 3
Dependent Claim
51 words
A system in accordance with claim 1 wherein there are four different terminations for each line comprising respectively open circuit, a direct connection to earth and connections to earth by way of respective rectifier elements posed in opposite senses, and each group of transistors comprises two transistors of opposite conductivity type.
Claim 4
Dependent Claim
41 words
A system in accordance with claim 2 wherein the alternating voltage is applied in common to the emitter electrodes of all four transistors while the base electrodes of the two transistors in each group are connected to the respective line wire.
Claim 5
Dependent Claim
22 words
A system in accordance with claim 2 wherein each of the four transistors is arranged when conducting to energize a respective relay.
Claim 6
Dependent Claim
30 words
A system in accordance with claim 2 wherein each of the four transistors is arranged when conducting to energize a respective relay by way of a respective transistor buffer stage.
Claim 7
Dependent Claim
36 words
A system in accordance with claim 4 wherein there are provided marking means operable in response to the energization of different combinations of said relays to apply marking potentials to different contacts of a final selector.
Claim 8
Dependent Claim
17 words
A system in accordance with claim 6 wherein the marking means comprises a pLurality of further relays.
Claim 9
Dependent Claim
56 words
A system in accordance with claim 1, wherein said means responsive to current flow through said transistors comprises logic means to enter into storage means signals representing the digit value of an operated pushbutton and there are provided means to generate a train of signalling impulses in dependence upon the signals entered in said storage means.
Claim 10
Dependent Claim
15 words
A system in accordance with claim 8 wherein said storage means comprises a binary counter.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-10-10 | 1976-04-10 | 1976-10-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-10 | 1980-04-10 | 1980-10-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-10 | 1984-04-10 | 1984-10-10 | $7700.00 | Window Closed / Lapsed |