The 3789B DS3 Transmission Test Set is a powerful test set offering outstanding monitoring and troubleshooting capabilities. A built-in demultiplexer allows it to perform measurements on both DS1 and DS3 signals from a DS3 access point. On equipment using C-bit parity frame format, the unit can measure the end-to-end performance of a transmission path in both directions simultaneously from a single access point. The instrument can operate with test patterns that are unframed or framed in M13 or C-bit parity format. A comprehensive error injection facility allows for stress-testing of equipment and interfaces. It can generate and detect the "DS3 Idle" signal.