Telephone line seizure circuit
First Claim
1. Telephone line seizure apparatus for a security alarm system including a system controller that is responsive to alarm signals from a plurality of distributed sensors, comprising:
- a) a telephone line having two conductors;
b) a first handset coupled in parallel to the two conductors;
c) a blocker circuit serially coupled to one conductor of said telephone line between said telephone line and the first handset for maintaining a short circuit condition and connection of the first handset to the telephone line in response to a ring signal or an off hook condition at the first handset; and
d) a line monitoring circuit for monitoring the condition of said telephone line and responsive to a signal from said system controller for short circuiting said telephone line and causing said blocker circuit to revert to an open circuit condition, whereby the first handset is disconnected and the system controller can seize said telephone line and initiate telephone communications, said line monitoring circuit comprising a plurality of relays coupled to respond to control signals from a microprocessor of said system controller wherein;
i) a first relay couples a capacitor across the two conductors of the telephone line for a predetermined period of time; and
ii) a second relay couples an isolation device for isolation and preventing the first handset from capturing the telephone line when the system controller is connected thereto.
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Accused Products
Abstract
A telephone system including circuitry for monitoring the "on hook" and "off hook" conditions of telephone handsets coupled to a system controller and disconnecting all off hook handsets from the telephone line. With the detection of an alarm condition at a security alarm system that requires a communication link, line seizure is effected via an SCR controlled seizure circuit serially connected between each distributed handset and the telephone line. The seizure circuit normally conducts when a connected telephone is off hook. Upon detecting an alarm, a line monitor momentarily shorts the telephone line to drive any conducting line seizure circuits into a non-conducting condition that is maintained sufficiently long to permit the system controller to gain control of the line. During controller communications, the handsets are also isolated from the telephone line. A local phone is also coupled to permit reprogramming if an inoperative line is detected. A speech interface facilitates system programming via a central station.
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Citations
20 Claims
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1. Telephone line seizure apparatus for a security alarm system including a system controller that is responsive to alarm signals from a plurality of distributed sensors, comprising:
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a) a telephone line having two conductors; b) a first handset coupled in parallel to the two conductors; c) a blocker circuit serially coupled to one conductor of said telephone line between said telephone line and the first handset for maintaining a short circuit condition and connection of the first handset to the telephone line in response to a ring signal or an off hook condition at the first handset; and d) a line monitoring circuit for monitoring the condition of said telephone line and responsive to a signal from said system controller for short circuiting said telephone line and causing said blocker circuit to revert to an open circuit condition, whereby the first handset is disconnected and the system controller can seize said telephone line and initiate telephone communications, said line monitoring circuit comprising a plurality of relays coupled to respond to control signals from a microprocessor of said system controller wherein; i) a first relay couples a capacitor across the two conductors of the telephone line for a predetermined period of time; and ii) a second relay couples an isolation device for isolation and preventing the first handset from capturing the telephone line when the system controller is connected thereto. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. Telephone line seizure apparatus for a telephone system including a system controller, comprising:
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a) a telephone line having two conductors; b) a plurality of telephone handsets coupled in parallel to the two conductors; c) a plurality of blocker circuits each comprising a rectifier coupled to one conductor of said telephone line and a switch coupled to said rectifier by a voltage divider coupled in parallel to a series connected current control element and SCR and including a capacitor coupled in parallel to a portion of said voltage divider for establishing a time delay, each of the blocker circuits serially coupled to the one conductor of said telephone line between the telephone line and an associated handset for maintaining a short circuit condition and connection of the associated handset to the telephone line in response to a ring signal or an off hook condition at the associated handset; and d) a line monitoring circuit for monitoring the condition of said telephone line and responsive to a control signal from said system controller for short circuiting said telephone line and causing said blocker circuits to revert to an open circuit condition for a time sufficiently long to permit the line monitoring circuit to ensure that all of the telephone handsets are in an on hook condition, prior to the line monitoring circuit seizing the telephone line and isolating each of the telephone handsets therefrom, whereby the handsets are disconnected and the system controller can seize said telephone line and initiate telephone communications. - View Dependent Claims (11, 12, 13)
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14. Telephone line seizure apparatus for a security alarm system including a system controller that is responsive to alarm signals from a plurality of distributed sensors, comprising:
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a) a telephone line having two conductors; b) a first handset coupled in parallel to the two conductors; c) a blocker circuit serially coupled to one conductor of said telephone line between said telephone line and the first handset for maintaining a short circuit condition and connection of the first handset to the telephone line in response to a ring signal or an off hook condition at the first handset; and d) a line monitoring circuit for monitoring the condition of said telephone line and responsive to an alarm reported to said system controller for short circuiting said telephone line and causing said blocker circuit to revert to an open circuit condition such that the first handset is disconnected and the system controller can seize said telephone line and initiate telephone communications, the line monitoring circuit further including a subcircuit responsive to a non-operational telephone line condition for coupling a second handset to the system controller, whereby the system controller can be re-programmed. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification