Supervision Device for Contact Sense Points
Original Publication Date: 1984-Dec-01
Included in the Prior Art Database: 2005-Feb-06
This article describes a supervision device which provides detection of line faults, such as short circuits, on sense or alarm lines that utilize normally closed circuits. The device disclosed herein allows the user to supervise contact sense lines when these lines support sensor devices utilizing normally closed (N.C.) sense switches or similar switch schemes. While this was possible in the past, it often required resistor networks at the sensor and its use was frequently negated by high loop resistance in the lines connecting the sensor to the central station, computer center, or like facility. In the present scheme the loop resistance is not critical, and with the values shown in Fig. 1, loops between 0 ohms and 300 ohms are easily tolerated. Referring to Fig.