Repeater Keying Line Control

A circuit for controlling timed functions in a repeater. The use of the new

Si fine, tics NE555 IC timers eliminates electronic and mechanical complications.

Every repeater has a neeJ for two basic I timing functions. The first is the delayed drop out. A short time delay between the release of the COR and the transmit Ier drop out is necessary to prevent the transmitter keying relays from chattering on a signal that is fluttering in and out of the i repeater receiver. This short delay, usually approximately two seconds, will prevent the annoying chattering noise and prolong the life of the equipment,

The second function is usually called the time-out-timer or transmit-in tervafetimer. Occasionally someone will accidentally or deliberately leave his transmitter keyed up on the input channel of the repeater. If the transmitter in the repeater is not rated for continuous service, it may overheat or be damaged. If for some reason, the repeater cannot be controlled under these conditions, this can cause severe anxiety for the person who must either wait for it to go away, or drive a hundred miles in the mountains at night to solve the problem.

Many repeater systems use surplus time delay relays, coffee pot trimmers, or other mechanical contrivances. These devices may be either unreliable or expensive.

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