High-voltage subscriber line interface LSIs

A high-voltage BORSHT LSI family for an all solid-state subscriber line interface circuit in a digital local switching system has been developed. The family consists of a 320 V dielectrically isolated RTLSI, a 60 V bipolar BSH-LSI, and a CMOS control LSI. Ringing, reverse, and network-test functions were implemented in the RT-LSI chip using a high-voltage current-controlled p-n-p-n-switch integration technology. Battery feed, supervision, and hybrid functions have been integrated into the BSH-LSI chip using a high-precision analog bipolar process technology. The CMOS logic LSI performs a digital interface function with the PCM highway, as well as a control function for the other LSIs. Using this BORSHT LSI family along with a codec, it has become possible to make a low-cost and small-size subscriber line interface circuit for central office use.