View source for Engineering:Four-wire terminating set

A '''four-wire terminating set''' (4WTS) is a [[Engineering:Balanced line|balanced]] [[Engineering:Transformer|transformer]] used to perform a conversion between [[Engineering:Four-wire circuit|four-wire]] and [[Engineering:Two-wire circuit|two-wire]] operation in telecommunication systems.
For example, a [[Engineering:Four-wire circuit|4-wire circuit]] may, by means of a 4-wire terminating set, be connected to a 2-wire [[Engineering:Telephone|telephone]] set. Also, a pair of 4-wire terminating sets may be used to introduce an intermediate 4-wire circuit into a [[Engineering:Two-wire circuit|2-wire circuit]], in which loop [[Repeater|repeater]]s may be situated to amplify signals in each direction without [[Positive feedback|positive feedback]] and oscillation. 

The 4WTS differs from a simple [[Engineering:Hybrid coil|hybrid coil]] in being equipped to adjust its impedance to maximize [[Engineering:Return loss|return loss]].

Four-wire terminating sets were largely supplanted by resistance hybrids in the late 20th century.

==References==

[[Category:Telephony equipment]]


{{Sourceattribution|Four-wire terminating set}}