Two-way calling public CT2 telepoint system

In most current implementations of CT2 telepoint systems, only handset initiated calls are allowed. This paper describes a design to allow two-way calling for the CT2 public telepoint system with minimal modifications to the current CT2 infrastructure and the public switched telephone network (PSTN). The design makes use of centralized databases in the home location register (HLR) and visitor location registers (VLR) to track the location of handsets. This location information is stored in the VLR and HLR, and is used by the PSTN to route incoming calls destined for CT2 handsets to the appropriate CT2 telepoint base station (TBS). The TBS connect to the PSTN local exchanges (LE) through the integrated services digital network (ISDN) basic rate interfaces (BRI) for fast out-of-band signaling. We present simulation results of the system with the objective of determining where congestion might occur within the system and to understand the impact of the new implementation on the PSTN. The results indicate that the performance of the system will be limited by the VLR processing speed and the number of ISDN BRI's connecting the ISDN front end (IFE) to the PSTN