Telecommunication switching system

A communication switching system, in addition to normal services i.e., voice, FAX, data, etc., provides secure bi-directional communication between the facilities of a utility and specialized voice and/or data CPE which are served by an on-premises Telemetry Interface Unit. A Central Office Service Unit (COSU), which is connected to a switching system by Utility Telemetry Trunks (UTT), is employed as an interface between utilities and one or more communication switching systems. The COSU provides detailed calling instructions and data which define the services to be rendered by the switching system. The detailed instructions serve to: define the source and character of the signals to be used to alert the TIU; sub-addresses of CPE served by a TIU; conduct of line supervision; permitted supervisory state of a called line at time of call to a TIU; broadcast of messages, etc.