American District Telegraph Company

James O Bean

Aaron A Galvin

James B Edson

A cable supervision system especially adapted for use in an intrusion alarm installation and which is capable of monitoring at a central control unit all lines of an interconnection cable for proper signal levels and balance. Under intended cable signal conditions a predetermined sensible impedance is provided which is monitored at the control unit. A monitoring circuit is coupled to the end of a system cable remote from the control unit, this circuit being operative to monitor the signal conditions of all lines of the cable. In response to proper signal conditions on the cable as determined by this monitoring circuit a predetermined impedance is provided which is sensed at the control unit to detect a change in impedance which would signal a tamper or cable failure alarm.

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Boston, MA, United States of America

James O Bean