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US3825897A Expired / Lapsed US ⏱️ 0.0 years remaining

Transmitter control circuit for alarm system

Assignee: ELECTRONIC SURVEILLANCE CORP L
•
Filing: 1973-09-24
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Granted: 1974-07-23
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Expires: 1993-09-24
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Abstract

Abstract In an alarm system having a plurality of stations connected to a single line, where each station has a transmitter which can transmit a pulsed signal to the line which is indicative of an alarm event at that station, it is important that ''''collisions'''' between signals from different stations on the same line be avoided. Line lock-out means are provided at each station to preclude transmission of a pulsed signal from that station when a pulsed signal from another station connected to the line is sensed; and the line lock-out means is provided with a timing circuit which operates to permit transmission from that station after a predetermined period of time following the last sensed pulse from another station on the line. Thus, the station may immediately transmit on the event of an alarm if sufficient time has passed since the last time a pulse from another station was sensed on the line; or the transmission is held off until that predetermined period of time follows the last sensed pulse on the line from another station. However, in the event of continual sensing of a line busy condition because of an intermittent fault on the line or a ''''runaway'''' transmitter at another station, each station will seize the line after a predetermined length of time has passed since the event of an alarm at that station, regardless of the condition of the line. Thus, the line lock-out circuitry will preclude transmission of a signal from a station for about 5 seconds after sensing any pulse from another station, but the line may be seized after 5 seconds from the last sensing of a pulse from another station. A 2 minute ''''override'''' timer operates to seize the line regardless of its condition, two minutes after an alarm event at that station, if the alarm signal has not already been transmitted.

Inventors

  • 👤 R Lawton

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-23 14:33
CPC Classifications
G; G08; G08B; G08B25/00; G08B25/01; G08B25/04

Claims Analysis

Total Claims: 7
Claim 1
Independent Claim 239 words
In an alarm system having a plurality of stations connected to a single line; each said station having alarm sensing means responsive to an alarm event, transmitter means for transmitting a pulsed signal to said line indicative of an alarm event at that station, means for sensing the presence on said line of a pulsed signal from any station connected thereto, and means to preclude transmission of a pulsed signal to said line when a pulsed signal from another station connected thereto is sensed; the improvement wherein: said means to preclude transmission of a pulsed signal to said line when a pulsed signal from another station connected thereto is sensed, is adapted to permit operation of said transmitter means after a first predetermined period of time following the last sensed pulse from another station connected to said line; and each said station further includes control and override means which is operative for a second predetermined period of time from the occurrence of an alarm event at a station to preclude operation of said transmitter means at that station in the event that said means for sensing continues to sense the presence of pulsed signals on said line throughout said second predetermined period of time, after which said override means is adapted to permit operation of said transmitter means at that station after said second predetermined period of time irregardless of the sensed presence of pulsed signals on said line.
Claim 2
Dependent Claim 239 words
In an alarm system having a plurality of stations connected to a single line; each said station having alarm sensing means responsive to an alarm event, transmitter means for transmitting a pulsed signal to said line indicative of an alarm event at that station, means for sensing the presence on said line of a pulsed signal from any station connected thereto, and means to preclude transmission of a pulsed signal to said line when a pulsed signal from another station connected thereto is sensed; the improvement wherein: said means to preclude transmission of a pulsed signal to said line when a pulsed signal from another station connected thereto is sensed, is adapted to permit operation of said transmitter means after a first predetermined period of time following the last sensed pulse from another station connected to said line; and each said station further includes control and override means which is operative for a second predetermined period of time from the occurrence of an alarm event at a station to preclude operation of said transmitter means at that station in the event that said means for sensing continues to sense the presence of pulsed signals on said line throughout said second predetermined period of time, after which said override means is adapted to permit operation of said transmitter means at that station after said second predetermined period of time irregardless of the sensed presence of pulsed signals on said line.
Claim 3
Dependent Claim 135 words
The alarm system of claim 1 where said means to preclude transmission of a pulsed signal to said line when a pulsed signal from another station connected thereto is sensed, includes first gate means having a first alarm input and a second trigger input, at least said second input having a predetermined voltage level at which said first gate may become operative to initiate operation of said transmitter means; said means for sensing the presence on said line of a pulsed signal from any station connected theretO, being connected to said second trigger input of said first gate and to an RC timer circuit to preclude acquisition of said predetermined voltage level by said second input for said first predetermined period of time following the last sensed pulse from another station connected to said line.
Claim 4
Dependent Claim 87 words
The alarm system of claim 2 where said control and override means includes second gate means having a first alarm input and a second trigger input, at least said second input having a predetermined voltage level at which said gate may become operative to initiate operation of said transmitter means; and an RC timer circuit connected to said second input and adapted to start timing said second predetermined period of time upon the occurrence of an alarm input signal at the first input of said second gate.
Claim 5
Dependent Claim 108 words
The alarm system of claim 3 where each first input of each of said first and second gates is connected to the other, and each is connected to a bistable latch adapted to switch to a first state and to pass an alarm input signal to said first inputs upon the occurrence of an alarm event at that station; and said bistable latch is connected to a circuit associated with said transmitter means to switch said latch to a second state and to remove said alarm input signal from said first inputs after said transmitter has transmitted a pulsed signal to said line indicative of said alarm event.
Claim 6
Dependent Claim 57 words
The alarm system of claim 1 where said means for sensing the presence on said line of a pulsed signal from any station connected thereto, includes RC filter networks to form a passband only for signals on said line of the pulse duration and frequency which are indicative of an alarm event at a station connected thereto.
Claim 7
Dependent Claim 69 words
The alarm system of claim 4 where said second input of said first gate is connected to the output of each said first and second gated through inverter means so that said first gate is operative to permit continued operation of said transmitter means when signals therefrom are sensed on said line, while an alarm signal continues to appear at the first input of said first and second gates.

References Cited (Backward Citations)

US3484771A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1977-07-22 1978-01-21 1978-07-23 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1981-07-22 1982-01-21 1982-07-23 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1985-07-22 1986-01-21 1986-07-23 $7700.00 Window Closed / Lapsed

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