US3920928A
Expired / Lapsed
US
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Line control circuit
Assignee: AT&T Inc
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Filing: 1974-03-29
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Granted: 1975-11-18
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Expires: 1994-03-29
Abstract
Abstract A key telephone system is disclosed that includes a clock for generating both flash and wink lamp signals and digital timing signals. The system also includes a plurality of line control circuits, each of which is associated with an individual telephone line and a plurality of key telephone sets, each of which is associated with one or more telephone lines. Thus the key telephone system includes a plurality of subsystems, each comprising a telephone line and the line circuit and elements of the key telephone sets associated with that telephone line. Each line circuit includes a ringing detector, loop current sensor, and hold bridge. In addition each line circuit includes a counter having a plurality of selected states that respectively correspond to individual operational modes of the subsystem. A first group of logic gates responds to the occurrence of conditions associated with a particular operation mode (i.e., presence of loop current and absence of A lead current associated with hold mode) by applying the digital timing signals of the clock to the counter and/or enabling the counter to be stepped in response to such signals toward the corresponding selected state. A second group of logic gates responds to the counter reaching that selected state, indicating the continuous existence of the associated conditions for a predetermined period of time, by placing the subsystem in the corresponding mode (i.e., applying hold bridge to the line and wink lamp signals to the sets).
Inventors
- 👤 Stephen Walter Lye
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 11:46
CPC Classifications
H; H04; H04M; H04M9/00; H04M9/002; H04M9/005; H04M9/006
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
108 words
A line control circuit for use in a telephone system comprising the line control circuit, and a telephone line and at least one telephone set associated with the line control circuit, the system having a plurality of operational modes, the line circuit comprising a counter activatable to a plurality of selected states, each of which corresponds to an operational mode of the system; means responsive to the occurrence of a condition associated with a particular mode for activating the counter to advance toward a corresponding selected state; and means responsive to the advancement of the counter to said selected state for placing the system in a corresponding mode.
Claim 2
Dependent Claim
108 words
A line control circuit for use in a telephone system comprising the line control circuit, and a telephone line and at least one telephone set associated with the line control circuit, the system having a plurality of operational modes, the line circuit comprising a counter activatable to a plurality of selected states, each of which corresponds to an operational mode of the system; means responsive to the occurrence of a condition associated with a particular mode for activating the counter to advance toward a corresponding selected state; and means responsive to the advancement of the counter to said selected state for placing the system in a corresponding mode.
Claim 3
Dependent Claim
37 words
A control circuit as in claim 1 wherein the condition responsive means advances the counter to a particular selected state only in response to the continuous existence of the associated condition for a predetermined period oF time.
Claim 4
Dependent Claim
115 words
A control circuit as in claim 1 wherein the system has operational modes of idle and ringing and the condition responsive means advances the counter responsive to the presence of ringing voltage on the associated telephone line while the system is in the idle mode, the counter being advanced to a selected state corresponding to the ringing mode responsive to the continuous presence of ringing voltage on the associated telephone line for a predetermined period of time, and means responsive to the counter advancing to said selected state while ringing voltage is present on the associated telephone line and the system is in the idle mode for applying a ringing signal to the associated set.
Claim 5
Dependent Claim
116 words
A control circuit as in claim 1 wherein the system has operational modes of idle and ringing and the condition responsive means advances the counter responsive to the presence of ringing voltage on the associated telephone line while the system is in the idle mode, the counter being advanced to a selected state corresponding to the ringing mode responsive to the continuous presence of ringing voltage on the associated telephone line for a predetermined period of time, and means responsive to the counter advancing to said selected state while ringing voltage is present on the associated telephone line and the system is in the idle mode for applying a lamp flashing signal to the associated set.
Claim 6
Dependent Claim
63 words
A control circuit as in claim 4 wherein the system has operational modes of idle, ringing-flashing, and flashing and the means responsive to the couner advancing to said selected state while ringing voltage is present on the associated telephone line and the system is in the idle mode for applying both a ringing and a lamp flashing signal to the associated telephone set.
Claim 7
Dependent Claim
51 words
A control circuit as in claim 5 further including means for resetting the counter responsive to the condition responsive means and the counter responsive means, the resetting means resetting the counter responsive to the presence of ringing voltage on the associated telephone line while the system is in the ringing-flashing mode.
Claim 8
Dependent Claim
99 words
A control circuit as in claim 6 wherein the condition responsive means advances the counter responsive to the absence of ringing voltage on the associated telephone line while the system is in the ringing-flashing mode, the counter being advanced to a selected state corresponding to the flashing mode responsive to the continuous absence of ringing voltage on the associated telephone line for a predetermined period of time, and means responsive to the counter advancing to said selected state while the system is in the ringing-flashing mode for terminating the application of the ringing signal to the associated telephone set.
Claim 9
Dependent Claim
98 words
A control circuit as in claim 7 wherein the condition responsive means advance the counter responsive to the presence of ringing voltage on the associated telephone line while the system is in the flashing mode, the counter being advanced to a selected state corresponding to the ringing-flashing mode responsive to the continuous presence of ringing voltage on the associated telephone line for a predetermined period of time, and means responsive to the counter advancing to said selected state while ringing voltage is present on the associated telephone line for reapplying the ringing signal to the associated telephone set.
Claim 10
Dependent Claim
92 words
A control circuit as in claim 7 wherein the condition responsive means advances the counter responsive to the absence of ringing voltage on the associated telephone line while the system is in the flashing mode, the counter being advanced to a selected state corresponding to the idle mode responsive to the continuous absence of ringing voltage on the associated telephone line for a predetermined period of time, and means responsive to the counter advancing to said selected state for terminating the application of the lamp flashing signal to the associated telephone set.
Claim 11
Dependent Claim
75 words
A control circuit as in claim 1 wherein the systeM has operational modes of idle and ringing and the condition responsive means includes means for detecting ringing voltage on the associated telephone line, the ringing detector providing a first signal when ringing voltage is present and a second signal when ringing voltage is absent, and input logic means that advances the counter responsive to the first signal while the system is in the idle mode.
Claim 12
Dependent Claim
109 words
A control circuit as in claim 10 wherein the counter is advanced to a selected state corresponding to the ringing mode responsive to the continuation of the first signal for a predetermined period of time, and the counter responsive means includes mode logic means comprising a first detector gate having a unique output responsive to the first signal of the ringing detector and the counter advancing to said selected state while the system is in the idle mode, the unique output serving to set a ring flip-flop, the ring flip-flop in the set condition enabling a ringer driver gate to apply a ringing signal to the associated telephone set.
Claim 13
Dependent Claim
62 words
A control circuit as in claim 11 wherein the system has operational modes of idle, ringing-flashing, and flashing and the mode logic means further includes a flash flip-flop that is set responsive to the setting of the ring flip-flop, the flash flip-flop in the set condition enabling a flash driver gate to apply a lamp flashing signal to the associated telephone set.
Claim 14
Dependent Claim
63 words
A control circuit as in claim 12 further including logic means for resetting the counter to 0 count responsive to the input logic means and the mode logic means, the reset logic means including a first reset gate for resetting the counter to 0 count responsive to the ring flip-flop being in the set condition and the first signal of the ringing detector.
Claim 15
Dependent Claim
98 words
A control circuit as in claim 13 wherein the input logic means advances the counter responsive to the ring flip-flop being in the set condition and the second logic signal of the ringing detector, and the mode logic means includes a second detector gate having a unique output responsive to the flash flip-flop being in the set condition and the counter advancing to a selected state corresponding to the flashing mode, the unique output of the second detector gate serving to reset the ring flip-flop, and the ring flip-flop in the reset condition disabling the ringer driver gate.
Claim 16
Dependent Claim
106 words
A control circuit as in claim 14 wherein the input logic means advances the counter responsive to the ring flip-flop being in the reset condition and the first signal of the ringing detector, and the mode logic means includes a third detector gate having a unique output responsive to the first signal of the ringing detector and the counter advancing to a selected state corresponding to the ringing-flashing mode, the unique output of the third detector gate serving to set the ring flip-flop, and the ring flip-flop in the set condition enabling the ringer driver gate to reapply the ringing signal to the associated telephone set.
Claim 17
Dependent Claim
97 words
A control circuit as in claim 14 wherein the input logic means advances the counter means responsive to the ring flip-flop being in the reset condition, the flash flip-flop being in the set condition, and the second signal of the ringing detector, and the mode logic means includes a third detector gate having a unique output responsive to the counter advancing to a selected state corresponding to the idle mode, the unique output of the third detector gate serving to reset the flash flip-flop, and the flash flip-flop in the reset condition disabling the flash driver gate.
Claim 18
Dependent Claim
169 words
A control circuit as in claim 1 wherein the system has operational modes of in-use and hold and the telephone set includes a signal lead, current being present on both the signal lead and the associated telephone line when the system is in the in-use mode and the signal lead being interrupted when the system is to be placed in the hold mode, and wherein the condition responsive means comprises input logic means including a first inpuT gate for advancing the counter responsive to the presence of line current on the associated telephone line while the system is in the in-use mode and reset logic means including a first reset gate for resetting the counter to 0 count responsive to the presence of current on the signal lead, whereby the presence of both line current and signal lead current results in the counter being continuously reset to 0 count and the termination of signal lead current and continued presence of line current results in the advancement of the counter.
Claim 19
Dependent Claim
107 words
A control circuit as in claim 16 wherein the counter is advanced to a selected state corresponding to the hold mode responsive to the continued absence of signal lead current and presence of line current for a predetermined period of time, and the counter responsive means includes mode logic means comprising a first detector gate having a unique output responsive to the continued presence of line current and the counter advancing to said selected state, the unique output serving to set a hold flip-flop, the hold flip-flop in the set condition enabling a hold bridge driver gate to connect a hold bridge across the associated telephone line.
Claim 20
Dependent Claim
32 words
The control circuit as in claim 18 wherein the hold flip-flop in the set condition also enables a wink driver gate to apply a lamp winking signal to the associated telephone set.
Claim 21
Dependent Claim
121 words
A control circuit as in claim 19 wherein the reset logic means includes a second reset gate for resetting the counter to 0 count responsive to the continued absence of signal lead current, presence of line current, and the hold flip-flop being in the set condition, and the input logic means includes a second input gate for advancing the counter responsive to the hold flip-flop whereby the absence of signal lead current and presence of line current while the system is in the hold mode results in the counter being continuously reset to 0 count and the absence of both signal lead current and line current while the system is in the hold mode results in the advancement of the counter.
Claim 22
Dependent Claim
104 words
A line control circuit as in claim 20 wherein the system further has an idle operational mode and the counter is advanced to a selected state corresponding to the idle mode responsive to the continued absence of line current for a predetermined period of time while the system is in the hold mode, and the mode logic means includes a second detector gate having a unique output responsive to the counter advancing to said selected state, the unique output serving to reset the hold flip-flop, and the hold flip-flop in the reset condition disabling the wink driver gate and the hold bridge driver gate.
Claim 23
Dependent Claim
125 words
A control circuit as in claim 19 wherein the input logic means includes a second input gate for advancing the counter responsive to the hold flip-flop being in the set condition, and the counter is advanced to a selected state corresponding to the in-use mode responsive to the continued presence of signal lead current for a predetermined period of time while the system is in the hold mode, the mode logic means including a second detector gate having a unique output responsive to the presence of signal lead current and the counter advancing to said selected state, the unique output serving to reset the hold flip-flop, and the hold flip-flop in the reset condition disabling the wink driver gate and the hold bridge driver gate.
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) | 1978-11-17 | 1979-05-19 | 1979-11-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-17 | 1983-05-19 | 1983-11-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-17 | 1987-05-19 | 1987-11-18 | $7700.00 | Window Closed / Lapsed |