Editing Four-wire terminating set

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A '''four-wire terminating set''' (4WTS) is a [[balanced line|balanced]] [[transformer]] used to perform a conversion between [[Four-wire circuit|four-wire]] and [[Two-wire circuit|two-wire]] operation in [[telecommunications|telecommunication]] systems.

For example, a [[Four-wire circuit|4-wire circuit]] may, by means of a 4-wire terminating set, be connected to a 2-wire [[telephone]] set. Also, a pair of 4-wire terminating sets may be used to introduce an intermediate 4-wire circuit into a [[Two-wire circuit|2-wire circuit]], in which loop [[repeater]]s may be situated to amplify signals in each direction without [[positive feedback]] and oscillation. 

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

Four-wire terminating sets were largely supplanted by [[resistance hybrid]]s in the late 20th century.

==References==
{{FS1037C MS188}}

[[Category:Telephony equipment]]

{{telephony-stub}}