A method for interface an IPABX and a local exchange includes the steps of: processing a call originated from an IPABX by a local exchange having one discernible individual by binding a plurality of data transmission lines, that is, a data transmission line trunk group; and processing a call destined...http://www.google.com.au/patents/US6917679?utm_source=gb-gplus-sharePatent US6917679 - Method for interface ISDN private automatic branch exchange and local exchange
