The Agilent HP 3777A is an HP-IB controlled Channel Selector. It provides test point access for maintenance and production testing of PCM and FDM telecommunications systems. The instrument contains two identical banks of relays, termed ?Transmit? and ?Receive?. Each bank comprises up to 30 balanced, bi-directional, two-pole changeover switches. The transmit bank enables switching of a single source to any one of up to 30 outputs. In the receive bank, any one of up to 30 inputs can be switched to a common output. To provide a quiet termination for telecommunications equipment, all unlocked channels are terminated in 600 Ohms in series with 2.2uF. The two switch banks are controlled independently via the HP-IB from the Agilent HP 3779A/B Primary Multiplex Analyzer (sold separately), a computer or a programmable calculator. For automatic test systems, The Agilent HP 3777A can scan, under external program control, through a number of channels in any desired sequence.