US3783195A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Plant telephone communication system
Assignee: Individual
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Filing: 1971-12-22
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Granted: 1974-01-01
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Expires: 1991-12-22
Abstract
Abstract This invention relates to a voice communication system for intra or interplant use and which operates with a constant D.C. line voltage with relatively lower currents to enable the lines to be much longer with less power loss. The line impedance may be of the order of 3,300 ohms. The system includes a complete handset amplifier and selector switch within the handset handle. A resistor in series with one of the lines provides energizing voltage to a silicon controlled rectifier which is also energized by an A.C. source to energize a relay or other controlled device. The system is basically a voltage system as compared to a regular telephone which is basically a current system.
Inventors
- 👤 P Day
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 13:19
CPC Classifications
H; H04; H04M; H04M9/00; H04M9/001
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
158 words
A voice communication voltage system comprising, a pair of line conductors energized by a constant voltage, direct current source; a plurality of telephone stations, each having high resistance of the order of thousands of ohms connected across said conductors, whereby voice signals impressed in said telephone stations will effect voltage modulations from zero to twice said D.C. voltage, a voltage divider network connected across said line conductors so as to provide a central group connection of zero volts, which is half way between the positive and negative terminals of said line conductors, a voltage regulating network having connected between said ground connection and one of said line conductors, a choke coil of high impedance and low D.C. resistance as well as means for limiting the current flow under short circuit conditions to a fraction of an ampere, whereby a voltage telephone system is provided wherein voice modulation will fluctuate from zero to about twice said D.C. line voltage.
Claim 2
Dependent Claim
158 words
A voice communication voltage system comprising, a pair of line conductors energized by a constant voltage, direct current source; a plurality of telephone stations, each having high resistance of the order of thousands of ohms connected across said conductors, whereby voice signals impressed in said telephone stations will effect voltage modulations from zero to twice said D.C. voltage, a voltage divider network connected across said line conductors so as to provide a central group connection of zero volts, which is half way between the positive and negative terminals of said line conductors, a voltage regulating network having connected between said ground connection and one of said line conductors, a choke coil of high impedance and low D.C. resistance as well as means for limiting the current flow under short circuit conditions to a fraction of an ampere, whereby a voltage telephone system is provided wherein voice modulation will fluctuate from zero to about twice said D.C. line voltage.
Claim 3
Dependent Claim
35 words
A voice communication system as recited in claim 1, wherein each of said high A.C. impedance is a choke coil and with said telephone stations will provide an overall resistance of about 3, 300 ohms.
Claim 4
Dependent Claim
53 words
A voice communication system as recited in claim 1, wherein said D.C. line voltage is about 125 volts and wherein the voltage across said telephone stations is of the order of 48 volts D.C., whereby modulations from voice signals will vary from zero to twice said 48 volts, namely, to about 96 volts.
Claim 5
Dependent Claim
54 words
A voice communication system as recited in claim 1, wherein said line voltage is of the order of 125 volts D.C. and wherein the voltage applied across each telephone station if of the order of 48 volts D.C. and wherein the D.C. resistance across each telephone station is of the order of 3,300 ohms.
Claim 6
Dependent Claim
139 words
A voice communication system as recited in claim 1, wherein said means for limiting the current flow comprises a zener diode connected between said ground connection and one terminal of said choke coil and includes a pair of transistors connected between the other choke coil terminal and a line conductor, forming an emitter follower circuit, and wherein the associated choke coil biases one of said transistors with D.C. current from a resistance connected across said one terminal of said choke coil and said line conductor while at the same time allowing voice signals on the line to be fed back to the base of said transistor so as to cancel out the inherent negative feedback of the circuit, with the end result of providing a very high source impedance limited only by the inductance of said associated choke coil.
Claim 7
Dependent Claim
35 words
A voice communication system as recited in claim 5, together with a safety diode in each of said line conductors to prevent any spurious spikes on the line from backing up into a telephone station.
Claim 8
Dependent Claim
123 words
A voice communication voltage system comprising a power line energized by constant voltage, direct current of the order of 125 volts and having a line impedance of the order of thousands of ohms, a page line and a party line, a plurality of separate stations interconnected by said power, page and party lines, each station including a loudspeaker having an amplifier connected to said page line and a handset including a handset preamplifier which is energized by the constant voltage, direct current, each handset including a selector switch for selectively connecting the handset to either said page line or to one of a plurality of party lines, each party line and page line including a solid state slave switch associated with said handset.
Claim 9
Dependent Claim
123 words
A voice communication voltage system comprising a power line energized by constant voltage, direct current of the order of 125 volts and having a line impedance of the order of thousands of ohms, a page line and a party line, a plurality of separate stations interconnected by said power, page and party lines, each station including a loudspeaker having an amplifier connected to said page line and a handset including a handset preamplifier which is energized by the constant voltage, direct current, each handset including a selector switch for selectively connecting the handset to either said page line or to one of a plurality of party lines, each party line and page line including a solid state slave switch associated with said handset.
Claim 10
Dependent Claim
68 words
A system as recited in claim 7 wherein said preamplifier is connected in series with a hookswitch and said selector switch, said preamplifier contained within said handset, said slave switches being selectively connected in series with said hookswitch and selector switch so that current will flow through only one slave switch at one time and thereby avoid cross talk because of uncompleted circuits through the otHer slave switches.
Claim 11
Dependent Claim
23 words
A system as recited in claim 8 wherein said hookswitch, selector switch and preamplifier are enclosed within the handle portion of said handset.
Claim 12
Dependent Claim
29 words
A system as recited in claim 8, together with a momentary switch in series with said selector switch and preamplifier and wherein said slave switches are silicon unilateral switches.
Claim 13
Dependent Claim
60 words
A voice communication system as recited in claim 7, comprising a resistor in series with one of the lines of said system energized by the constant D.C. line voltage, a silicon controlled rectifier in series circuit relationship with said resistor, and a controlled relay in series with and controlled by said rectifier and energized by a separate A.C. power source.
Claim 14
Dependent Claim
115 words
A voice communication system as recited in claim 7, wherein said constant D.C. line voltage is applied to a voltage dividing and electronic choke network to provide a center voltage point which is grounded midpoint said D.C. plus and negative supply lines, a pair of capacitors, each connected between said center voltage point and one of the D.C. supply lines, a resistor bridging each capacitor to bleed the charge of the bridged capacitor when power is removed, and a zener diode, inductor and diode means serially bridging a second resistor connected to a power line in series with said zener diode for regulating the voltage of said D.C. supply line and for limiting line current.
Claim 15
Dependent Claim
47 words
A system as recited in claim 12 together with a transistor emitter follower circuit connected between the terminal of each inductor closest said zener diode and one of said D.C. lines and in series with a line resistor bridged by said diode means and by a capacitor.
Claim 16
Dependent Claim
28 words
A system as recited in claim 12, wherein said diode means includes a light emitting diode which, when conducting, will indicate a short-to ground or current overload fault.
Claim 17
Dependent Claim
31 words
A system as recited in claim 14, including a safety diode in series with each of said D.C. supply lines for preventing spurious voltage spikes from backing up into the system.
Claim 18
Dependent Claim
31 words
A system as recited in claim 7, wherein a Page line muting circuit is connected across said Page line to silence all said loudspeakers when said handsets are not in use.
Claim 19
Dependent Claim
97 words
A system as recited in claim 7, said muting circuit comprising a resistor and capacitor connected across said Page line, a second capacitor selectively connectable across said Page line, a Page line resistor and transistor means connected therewith so that when line current flows through said Page line resistor, the line impedance will be of the order of 3,300 ohms, and when no current is flowing through said Page line and Page line resistor, said last mentioned capacitor will be connected driectly across the line by said transistor means to lower the line impedance to approximately zero.
Claim 20
Dependent Claim
45 words
A system as recited in claim 17, together with diode means connected across said Page line resistor to limit the voltage drop thereacross and prevent excessive line losses across said Page line resistor when a number of handsets are on the line at one time.
Claim 21
Dependent Claim
27 words
A system as recited in claim 18 together with a Zener diode connected across said first mentioned resistor and capacitor for clipping off excessively high voltage spikes.
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) | 1976-12-31 | 1977-07-02 | 1978-01-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-12-31 | 1981-07-02 | 1982-01-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-12-31 | 1985-07-02 | 1986-01-01 | $7700.00 | Window Closed / Lapsed |