The original MFJ-1708 series used one relay and wires to connect the SO-239s. The new B-series uses four relays and connectors on a single pc board. This gives you > 50 dB isolation at 300 MHz and > 68 dB at 50 MHz. SWR < 1.16:1 at 50 MHz
and >< 1.75:1 at 450 MHz at the transmit port. Mute output is a selectable short or open to ground. Use boat anchors or modern receivers or key a linear amplifier. Receiver input protection prevents overload from nearby high power
signals and from receive to transmit. A hybrid splitter on SDR models reduces loading effect and gives > 15 dB isolation between the SDR REC and XCVR ports to reduce interference.