Communications: electrical – Condition responsive indicating system – With particular system function
Patent
1982-09-30
1984-08-28
Crosland, Donnie L.
Communications: electrical
Condition responsive indicating system
With particular system function
340505, 3408251, 34082554, 34087009, 34087013, 179 5R, G08B 2600, H04Q 900
Patent
active
044686552
ABSTRACT:
A multiplex security system provides two-way data communications between a local panel and multiple microprocessor-based remote panels interconnected over a common data transmission line. A second line provides two-way voice communications between the local and remote panels with automatic forwarding by an audio/data control selector to a central control unit via a single telephone line. Two additional lines provide a common ground and transmit DC power from the local to the remote panels. The remote panels include bus drivers connected to the communications line for transmitting both ASCII digital data messages and a higher voltage request or SRQ signal to the local panel when the remote panel has a message to transmit. The local panel includes two separate receivers for distinguishing the request signal from digital data and a bus driver for transmitting data. The local panel transmits a grant message which is superimposed over the request signal, reducing its voltage level to zero. The remote panel has a receiver for receiving ASCII data from the local panel and for sensing the reduced voltage level to turn off the request signal. The remote panels are assigned priorities by setting different switch numbers in each panel. The switch numbers correspond to unique brief time slots in which each of the remote panels can commence transmitting. Following a grant command, the remote panels count time slots. None can respond until the count equals its respective switch number, and then only if another panel has not already commenced transmitting.
REFERENCES:
patent: 3978468 (1976-08-01), Bond et al.
patent: 3990075 (1976-11-01), Schmitz et al.
patent: 4040013 (1977-08-01), Carlson
patent: 4097690 (1978-06-01), Kuntz et al.
Crosland Donnie L.
Nel-Tech Development, Inc.
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