<communications> A restored polar signal, wideband data loop digital transmission facility for use with 303-type data stations, for serial signals synchronized to clock rates of 19.2, 40.8, 50.0, 230.4 or 460.8 kilobits per second. In its originally intended use, the 1.544 megabit per second T-1 line bit stream carried 24 pulse-code modulated, time-division multiplexed speech signals each encoded in 64 kilobit per second streams, leaving 8 kilobits per second of framing information which facilitates the synchronization and demultiplexing at the receiver.
Asynchronous signals can be transmitted via a standard which encodes each change of level into three bits; two which indicate the time (within the current synchronous frame) at which the transition occurred, and the third which indicates the direction of the transition. Although wasteful of line bandwidth, such use is usually only over small distances.
T-1 lines are made free of direct current signal components by in effect capacitor coupling the signal at the transmitter and restoring that lost component with a "slicer" at the receiver, leading to the description "restored polar".
Contrast DS1.
[Telecommunications Transmission Engineering, Vol. 2, Facilities, AT&T, 1977].
(21 Mar 1996)