A method and apparatus for transferring data between telephony communications lines having different frame transmission rates. A downlink data frame according to a first protocol (e.g. a ROLMlink frame) is transmitted, at a first data rate, from a private branch exchange (PBX) to a telephone's network...http://www.google.de/patents/US5287352?utm_source=gb-gplus-sharePatent US5287352 - Method and apparatus to reduce register overhead in a serial digital interface
