The TRip-S is a purpose built IP device designed specifically for the PMR system suppliers and PAMR Trunk Radio operators or service providers which now has the added option of a signalling interface to make the TRip-S unit even more flexible. The added signalling module gives the system designer the options of decoding over the air signalling at the base station and relaying the messages over the IP link as a virtual serial connection. The unit now also provides line keying such as M80 or Motorola compatible tone signalling for connecting to existing line controlled systems. The TRip-S provides the interface to analogue base stations for the TRICX IP based communication switch.