Common control

In telecommunication, a common control is an automatic telephone exchange arrangement in which the control equipment necessary for the establishment of connections is shared by being associated with a given call only during the period required to accomplish the control function for the given call. The first examples deployed on a major scale were the Director telephone system in London and the panel switch in the Bell System. Direct control telephone exchanges became rare in the 1960s, leaving only common control ones.

Note: During the 1980s, common control exchanges became stored program control exchanges, using common-channel signaling in which the channels that are used for signaling, whether frequency bands or time slots, are not used for message traffic. Specifically, the systems which have control subsystem as an integral part of the switching network itself, are known as direct control switching systems. Control subsystem permits interaction with the switching system for the maintenance and administrative purposes. But the systems in which the control subsytem is outside the switching network are known as Common control systems. Strowger exchanges are usually direct control systems, whereas crowbar, electronic exchanges including all stored program control systems are common control systems. Common control is also known as indirect control or register control.

References

 This article incorporates public domain material from Federal Standard 1037C. General Services Administration. Archived from the original on 2022-01-22. (in support of MIL-STD-188).