System for providing access to digitally encoded communications in a

Abstract

A distributed switching network (switch) routes audio and control signals throughout the switch from various audio sources to one or more audio destinations. Audio sources such as mobile/portable radio units (via RF repeater transmitters), dispatch consoles, and landline telephone subscribers (via the central telephone switching network) are preassigned and routed onto an audio channel (i.e. a time slot) on a time division multiplexed (TDM) audio bus through a corresponding interface module. These interface modules broadcast digitized audio and data signals to all other interface modules over their preassigned TDM bus slot. Audio routing is performed to the audio destinations through corresponding interface modules that selectively 'listen' to active TDM network channels. A digital voice interface module is provided in the switch to permit audio sources/destinations otherwise lacking certain digital processing capabilities (e.g. encryption/decryption) to participate in such digitally based calls. As a result, console operators and/or landline telephone subscribers may originate and receive digitally encoded calls without themselves having digital encoding/decoding capabilities.