In most current implementations of CT2 telepoint systems, only handset
initiated calls are allowed, This paper describes a design to allow t
wo-way calling for the CT2 public telepoint system with minimal modifi
cations to the current CT2 infrastructure and the public switched tele
phone 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 store
d 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 statio
n (TBS). TBS connect to the PSTN local exchanges (LE) through the inte
grated services digital network (ISDN) basic rate interfaces (BRI) for
fast out-of-band signaling. We present simulation results of the syst
em with the objective of determining where congestion might occur with
in the system and to understand the impact of the new implementation o
n the PSTN, The results indicate that the performance of the system wi
ll be limited by the VLR processing speed acid the number of ISDN BRI'
s connecting the ISDN front end (IFE) to the PSTN,