The Hull Speed Asynchronous to Synchronous model 4 (A/S-4) enables an asynchronous terminal to communicate with a synchronous modem or multiplexer.
The A/S-4 is designed with an auto rate sensor, which automatically determines and adjusts to the DCE data rate. The A/S-4 has a dynamic operating range of 1200 to 38,400
bps. In addition to the autobaud, the A/S-4 can tolerate DTE data rates of -2.5% below and +2.3% above the DCE clock rate.