GB1363329A - Telephone exchange with video sets - Google Patents

Abstract

1363329 Automatic exchange systems INTERNATIONAL STANDARD ELECTRIC CORP 25 May 1972 [29 May 1971] 24691/72 Heading H4K In a telephone exchange including some video substitutions, video connections are established over a separate video network, only if a common control unit after receiving the dialled designation of a wanted subscriber determines that both subscribers are entitled to a video service. In the P.A.B.X. shown, substations T may or may not have video equipment F. On initiation of a call a part connection is established via a two-wire audio-switching network KF to an internal link IVS. When the dialled wanted extension number has been received by the common control S, the control determines whether both extensions are entitled to video service. If either extension is not so entitled an audio only connection is completed back through the network KF to the called extension. If both extensions are entitled to video service the existing part connection is released and a connection is established from the line circuit TS via a six-wire audio/video network FKF to an audio/video internal link and then back through that network to the called extension. Audio calls can be connected to the local exchange via exchange links AVS.