Ringdown: In telephony, 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 (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. 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 drop to fall "down" at the central office switchboard, marked with the number of the line to which the magneto telephone instrument was connected. The last ringdown telephone exchange in the United States was located at Bryant Pond, Maine, had 400+ subscribers, and converted to dial service in October 1983. In telecommunication, Telephony encompasses the general use of equipment to provide voice communication over distances. ... Telecommunication In telecommunication, the term signaling has the following meanings: The use of signals for controlling communications. ... The telephone or phone (Greek: tele = far away and phone = voice) is a telecommunications device which is used to transmit and receive sound (most commonly voice and speech) across distance. ... A telephone line (or just line) is a single-user circuit on a telephone communications system. ... Relay is also the name of a series of medium-altitude satellites; the first of which was launched in 1962. ... A drop may be: a drop, unit of measure of volume a drop (or droplet) of liquid, such as raindrops causing a rainbow, or forming clouds or fog a drop or dropout in telecommunications, such as in losing a signal, or as in a wire dropped-down from a ceiling... The word operation can mean any of several things: The method, act, process, or effect of using a device or system. ... A dial is a generally a flat disk, often with numbers or similar markings on it, used for displaying the setting or output of a timepiece, radio or measuring instrument In telephony and telecommunications in connection with a telephone, a dial refers, in older telephones, to a rotating disk with... Signaling or signal may mean: Look up signal and signaling in Wiktionary, the free dictionary. ... Telephone switchboard, 1974 A switchboard (also called a manual branch exchange) is a device used to manually connect a group of telephones from one to another or to an outside connection. ... In the field of telecommunications, a central office or telephone exchange houses equipment that is commonly known as simply a switch, which is a piece of equipment that connects phone calls. ...

Source: from Federal Standard 1037C and from MIL-STD-188 Federal Standard 1037C entitled Telecommunications: Glossary of Telecommunication Terms is a U.S. Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended. ... MIL-STD-188 is a series of U.S. military standards relating to telecommunications. ...