A junctor is a circuit used in analog

telephone exchanges telephone exchange, telephone switch, or central office is a telecommunications system used in the public switched telephone network (PSTN) or in large enterprises. It interconnects telephone subscriber lines or virtual circuits of digital syste ...

, including the Number One Crossbar Switching System,

Number Five Crossbar Switching System The Number Five Crossbar Switching System (5XB switch) is a telephone switch for telephone exchanges designed by Bell Labs and manufactured by Western Electric starting in 1947. It was used in the Bell System principally as a Class 5 telephone swi ...

1ESS switch The Number One Electronic Switching System (1ESS) was the first large-scale stored program control (SPC) telephone exchange or electronic switching system in the Bell System. It was manufactured by Western Electric and first placed into servi ...

and other switches. In early electromechanical switches, a "district junctor" handled supervision and talk battery duties for outgoing calls, similar to the duties of the

cord circuit In telecommunication, a cord circuit is a switchboard circuit in which a plug-terminated cord is used to establish connections manually between user lines or between trunks and user lines. A number of cord circuits are furnished as part of the sw ...

of manual exchanges. The junctors for incoming calls were simple three-wire connections between the incoming frame and the line frame. In the later electromechanical

5XB switch The Number Five Crossbar Switching System (5XB switch) is a telephone switch for telephone exchanges designed by Bell Labs and manufactured by Western Electric starting in 1947. It was used in the Bell System principally as a Class 5 telephone swi ...

, junctors only consisted of three wires to connect the two legs of a call: the line and the trunk, of which the latter supplied all talk battery and supervision. Stored-program analog switches such as the

, had both simple wire junctors and circuit junctors. Circuit junctors were in the form of plug-in circuit boards to provide talk battery and supervision for intraoffice calls and were closely similar to intraoffice trunk packs, with two scan points and two signal distributor points per circuit, two circuits per plug-in pack. Wire junctors were two-wire connections between trunk nets and other trunk nets or line nets. When

three-way calling In human sexuality, a threesome is commonly understood as "a sexual interaction between three people whereby at least one engages in physical sexual behaviour with both the other individuals". Though ''threesome'' most commonly refers to sexua ...

was introduced, three-port conference trunks were used, which only appeared on trunk nets. All junctors appeared in subgroups of sixteen on plugs or jacks at the Junctor Grouping Frame, where as many subgroups as required were plugged into other trunk nets, line nets, or circuit junctor frames.

References

Telephony equipment {{telephony-stub