Graded service telephone exchange system - identifies authorisation of subscriber connected to branch exchange connected to local exchange

摘要

The telephone exchange system has authorisation data for subscribers connected to a private branch exchange kept at a local exchange. All exchange lines have uniform authorisation can be extended or removed for any single subscriber. Subscribers are identified by special codes using an identification process executed for forming a connection in the branch exchange between calling subscriber and exchange line. The special codes are sent to the local exchange once the exchange line has been siezed.