2m / 70cm Duplexer
This duplexer is a passive device that has a series of inductance coils and capacitors that act as a band-pass filter.
It can be used in two different ways. The diplexer can also be used to separate VHF transmissions from UHF transmissions so that one transceiver can be connected to two antennas.
As a passive device this 'duplexer' does not differentiate between input and output. Therefore you can either connect one radio to two atennas, or two radios (operating on different bands) to one multi-band antenna. The diplexer will simultaneously pass RF in both directions through the common connector while the band-pass filters provide a high degree of isolation between ports.