Line monitor for two wire data transmission
First Claim
1. An alarm system for detecting and warning of the presence of alarm and trouble conditions in transponder units located in a plurality of zones, comprising:
- a loop controller having a plurality of signal/power supply lines, including a wiring pair, connected to the respective units;
a module, including a microcontroller, connected in each of said predetermined zones to said plurality of lines, said module being capable of initiating communication of the alarm and trouble conditions of said circuits to said loop controller;
a plurality of outgoing circuits extending from said microcontroller, and means within said microcontroller for selectively operating said circuits in a variety of modes; and
means, including a connection extending from said microcontroller to a portion of said selectively operated circuits .and a line, for monitoring the line voltage such that the variable state of that voltage is accurately known, including means for obtaining a resultant monitoring current, which is indicative of the presence of alarm and trouble conditions, strictly as a function of the impedance across said wiring pair, and not as a function of the source voltage.
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Accused Products
Abstract
A line monitor uses two wire data transmission in a fire alarm and detection system. A line voltage monitoring mechanism is within each wiring/contact monitoring circuit such that the exact value at any time of varying source voltage is known. The monitoring current resultant from the monitoring arrangement is strictly a function of impedance and not a function of source voltage because a line-monitoring scaling factor is incorporated into the final calculation. The monitoring scheme also results in the alarm and trouble voltage thresholds being suitably altered to take account of changed line voltage conditions.
42 Citations
5 Claims
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1. An alarm system for detecting and warning of the presence of alarm and trouble conditions in transponder units located in a plurality of zones, comprising:
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a loop controller having a plurality of signal/power supply lines, including a wiring pair, connected to the respective units; a module, including a microcontroller, connected in each of said predetermined zones to said plurality of lines, said module being capable of initiating communication of the alarm and trouble conditions of said circuits to said loop controller; a plurality of outgoing circuits extending from said microcontroller, and means within said microcontroller for selectively operating said circuits in a variety of modes; and means, including a connection extending from said microcontroller to a portion of said selectively operated circuits .and a line, for monitoring the line voltage such that the variable state of that voltage is accurately known, including means for obtaining a resultant monitoring current, which is indicative of the presence of alarm and trouble conditions, strictly as a function of the impedance across said wiring pair, and not as a function of the source voltage.
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2. An alarm system as defined in claim 1, in which said line for monitoring the line or source voltage also extends from an input terminal on said microcontroller to a node on said portion of said selectively operated circuits.
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3. An alarm system as defined in claim 2, in which a pair of input connections are made to other terminals of said microcontroller for sensing whether or not alarm or trouble conditions are present in said circuits.
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4. An alarm system as defined in claim 3, in which means are provided within said microcontroller for adjusting the alarm and trouble thresholds to which the microcontroller responds so that said thresholds have a fixed relationship or fixed ratio with respect to the line voltage.
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5. An alarm system as defined in claim 1, further comprising a plurality of respective devices in said selectively operated circuits.
Specification