Processor-to-processor communications protocol for a public service trunking system

In a digitally trunked radio frequency repeater system of the type including plural RF repeater transceivers 177 communicating via radio frequency channels with mobile radio transceivers 152, said repeater transceivers being controlled by a site controller 410 which communicates control information with a dispatch console 102 over a downlink 103, the application discloses a method of operating said system comprising: communicating digital control signals between said repeater RF transceivers 177 and said mobile radio transceivers 152 via said radio frequency channels using a synchronous serial communications protocol; and communicating digital control signals between said site controller 410 and said dispatch console 102 over a telephone line data link 103 using said same synchronous serial communications protocol. A second invention is described, Fig - 2, (not shown).