The SDA-5500 is a rack-mountable headend Forward Sweep Transmitter for use with field CATV Receivers. The unit injects low-level signals in the forward downstream path, inserting signals in vacant channel or spectrum areas allowing a complete check of the system’s frequency response. The SDA-5500 also monitors the cable systems carrier levels in occupied spectrum areas for use in the non-interfering Sweepless Sweep where the carrier itself is used as the test signal. The SDA-5500 sends headend signal level readings to downstream receivers. When tuned to a specific channel, the unit provides information on Tuned Channel, Video Frequency and Level, Audio Frequency and Level, and Video and Audio Carrier Level Differences.