Automatic synchronous/asynchronous modem

摘要

There is disclosed an arrangement which enables a single modem port to be used for either synchronous or asynchronous data transmission, with no manual changes required. The modem determines whether the incoming call is synchronous or asynchronous by detecting the presence (or absence) of SYNC characters in the data stream immediately after handshaking. Once a determination has been made, the modem options itself accordingly for synchronous or asynchronous data handling. This arrangement eliminates the need for separate central office lines for synchronous and asynchronous data applications.