A modem includes an electronic processor responsive to a context signal and operable in alternative processing contexts identified by the context signal. First and second registers are connected to the electronic processor to participate in one processing context while retaining information from another...http://www.google.com.hk/patents/US5319792?utm_source=gb-gplus-share專利 US5319792 - Modem having first and second registers enabling both to concurrently receive identical information in one context and disabling one to retain the information in a next context
