... service: FXS, FXO, Ethernet, V.35, X.21, V.24, G703 (64K), RS-232, RS422, RS485, 2/4 wire voice band ... .21 synchronization data modular V24 V.24 synchronization data modular G703 G703 (64K) codirection synchronization data modular 232 RS-232 asynchronous data ...