GAO's V.42 software is designed for optimum asynchronous-to-synchronous conversion as well as error detection and retransmission of damaged data. The ITU-T V.42 standard addresses two major problems for asynchronous devices: an asynchronous-to-synchronous conversion protocol and a sophisticated error-detection process for asynchronous systems. This recommendation contains an HDLC-based protocol referred to as the Link Access Procedure for Modems (LAPM).
Features of V42 Error Correction Protocol
Link control protocol for the sequencing and flow control of the traffic
Cyclic redundancy check for error detection
V.14 for asynchronous-to-synchronous conversion operations
Inter-working in the non-error-correcting mode with V-Series DCEs that include asynchronous-to-synchronous conversion according to Recommendation V.14
Synchronous transmission through the conversion of start-stop data
Initial handshake in start-stop format minimizes disruption to the DTEs