Meaning of RINGDOWN in English

In telephony , a method of signaling an operator in which telephone ringing current is sent over the line to operate a lamp and cause the drop of a self-locking relay . ( 188 ) Note 1: Ringdown (a) is used in manual operation , as distinguished from dialing , (b) uses a continuous or pulsed ac signal transmitted over the line, and (c) may be used with or without a switchboard . ( 188 ) Note 2: The term "ringdown" originated in magneto telephone signaling in which cranking the magneto in a telephone set would not only " ring " its bell but also cause a lever to fall "down" at the central office switchboard.

Telecommunication standard terms English vocab.      Английский словарь стандартных телекоммуникационных терминов.