Redundant Power and Communications on a Single Cable (From Carnahan Conference on Security Technology, P 85-89, 1987, John S. Jackson and R. William De Vore, eds. -- see NCJ-118105)

• NCJ Number: 118120
• Author(s): J K Lynn
• Date Published: 1987
• Length: 5 pages
• Publication Format: Document
• Publication Type: Report (Technical)
• Language: English
• Country: United States of America

Annotation

This paper presents a method for providing redundant power and communications on a loop of cable which is able to link 24 or more sensor systems.

Abstract

The power uses a central battery or Uninterruptible Power Supply (UPS), and is distributed by direct current. A redundant power loop of 100 percent is three AWG 10 conductors and two shielded pairs, coextruded in a buriable sheath. Voltage drops will be compensated by individual AC/DC converters, therefore, cutting a combination cable does not disable a looped system. A short from any single power conductor to ground shall cause a circuit breaker at the head-end to trip, thus removing the fault from the system. Diodes at each processor isolate the fault, and supervision circuits signal the voltage imbalance. A bidirectional, multiplexed, addressable transponder at each sensor accepts eight alarm inputs. If a local failure occurs, that transponder is bypassed and head-end cable power of 48 volts DC, trickle charges a 48-volt battery. AC to DC converters with a nominal input voltage of 48 VDC (plus or minus 50 percent) provide a regulated 15 VDC at up to 0.8 amps at each processor. Local backup batteries may be provided at each sensor to allow redundant backup. 8 figures, 6 references. (Author abstract modified)