In addition to single-line IDA, British Telecom will also offer multi-line IDA service at two Mbps, principally for use with PBXs designed to operate with ISDN networks, and termed ISPBXs. Initial tariffs call for a connect charge of $195 for single-line IDA and an annual rental charge of $224.
The ISPBXs will use a common channel signaling system called DASS II (Digital Access Signaling System), until CCITT standards become available.