ITU-T Q.120-Q.139-1988
Specifications of Signalling System No. 4 Study Group XI [Superseded: ITU-T Q.121 ITU-T Q.122 ITU-T Q.123 ITU-T Q.124 ITU-T Q.125 ITU-T Q.126 ITU-T Q.127 ITU-T Q.128 ITU-T Q.129 ITU-T Q.130 ITU-T Q.131 ITU-T Q.133 ITU-T Q.135 ITU-T Q.136 ITU-T Q.137 ITU-T

Standard No.

ITU-T Q.120-Q.139-1988

Release Date

1988

Published By

International Telecommunication Union (ITU)

Latest

ITU-T Q.120-Q.139-1988

Scope

This signal is transmitted at the beginning of a call to initiate circuit operation at the incoming end of an international circuit. The seizing signal can also perform switching functions and two different types of seizing signal are provided for this purpose, viz: the terminal seizing signal, which can be used at the incoming international exchange, to seize equipment used exclusively for switching the call to the national network of the incoming country; the transit seizing signal, which can be used in the exchange at the incoming end of the international circuit to seize equipment used exclusively for switching the call to another international exchange.

ITU-T Q.120-Q.139-1988 history

• 1988 ITU-T Q.120-Q.139-1988 Specifications of Signalling System No. 4 Study Group XI [Superseded: ITU-T Q.121 ITU-T Q.122 ITU-T Q.123 ITU-T Q.124 ITU-T Q.125 ITU-T Q.126 ITU-T Q.127 ITU-T Q.128 ITU-T Q.129 ITU-T Q.130 ITU-T Q.131 ITU-T Q.133 ITU-T Q.135 ITU-T Q.136 ITU-T Q.137 ITU-T