Importance

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Abstract

The system includes a number of spaced apart key stations which a watchman is to visit on a tour of an area. A portable unit is provided with two AND circuits. Upon starting a tour, one of the AND circuits sets a number of timers, a first one of the timers starts running providing a signal to a prealarm sound-producing device on the portable unit unless the first timer has been reset by the completion of the second AND circuit by having inserted all of the keys and turning them. At the same time, the first timer starts a second timer running. The second timer provides a delay which allows the watchman a few more minutes to complete his tour. If he fails, a third timer feeds a fault signal to a counter in the portable unit and also triggers a further audible alarm device on the portable unit and at the same time resets all the timers in the portable unit. A coder is provided in the portable unit which provided an output, via a plug and jack arrangement, to a decoder which resets a timer at a base station. Otherwise, this timer will effect the enabling of an audible alarm at the base station indicating either that all keys had not been turned or that the watchman has not returned.

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First Claim