Frontline Test Equipment Inc., Charlottesville, VA, offers Serialtest v6.6 with Modbus, which is a PC-based serial communications protocol analyzer. The software includes decoders for serial PPP, SLIP, TCP/IP, Modbus RTU, and ASCII, as well as FrameDecoder for decoding proprietary or enhanced protocols. Other features include asynchronous high-speed capability, Spy mode to monitor a PC's own serial communications internal device, and Frame Display to show detail of errors. A synchronous version of Serialtest is available, but requires a ComProbe serial interface device. It supports Monosync, Bisync, HDLC, SDLC, X.25, SNA, and Frame Relay.