Intrinsically safe communication systems

Details Intrinsically safe communication systems Intrinsically safe communication systems

1975-05-01

1976-12-14

Robinson, Thomas A.

317 16, H04M 100, H02H 320

Patent

active

039977331

ABSTRACT:
The invention is a communications and tone control system for use between safe and hazardous areas. The invention's field terminals operate in hazardous areas and are limited to low, intrinsically safe power levels by the use of zener barriers and current limiting resistors. The limited D.C. electrical power supplied to the field terminal's amplifier is modulated by field initiated communication and control signals. The resulting duplex transmission allows a strong information carrying signal and amplifier power to pass through a single twisted pair at intrinsically safe power levels. All field stations are connected in parallel to a central control system in a safe area allowing the communication system to operate redundantly. The field stations can be selectably connected to a plurality of output devices by tone controlled switching circuits.

REFERENCES:
patent: 2285022 (1942-06-01), Edwards
patent: 3181033 (1965-04-01), Bakker
patent: 3558830 (1971-01-01), Bender
patent: 3624449 (1971-11-01), Morgan
patent: 3631264 (1971-12-01), Morgan
patent: 3813578 (1974-05-01), Tiffany

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