1) Communication circuit
Found on
https://www.crosswordclues.com/clue/ringdown
In telephony, ringdown is a method of signaling an operator in which telephone ringing current is sent over the line to operate a lamp or cause the operation of a self-locking relay known as a drop. Ringdown is used in manual operation, as distinguished from automatic signaling by dialing a number. The signal consists of a continuous or pulsed alt...
Found on
http://en.wikipedia.org/wiki/Ringdown
(telephone) An Automatic ringdown circuit consists of two phones at different locations. When either phone goes off-hook, the one at the other end instantly rings.
Found on
http://www.translationdirectory.com/glossaries/glossary102.htm
No exact match found.
