1、Increases call distance over 10km, two‑way communication (receiving and transmission). 2、Simple operation, no power is required, no replacement of any part of the intercom is required, all you need is two hand‑held interphones and connect the cable to the external micron/SPK ports (5mm and 5mm). 3、Transponder downlink forwarding (differential and conventional relay stations), with one machine as the signal for the uplink receiver and one machine as the signal downlink transmitter. Relay purpose has been achieved. 4、Two‑way forwarding, receiver machine, B machine transmission, B machine receives, machine transmits, realize the two‑way forwarding function. 5、Relay box for the audio trigger mode, the received signal intercom has maximum volume when using. 1 x Intercom Relay Box2 x Connection Cable  Condition: 100% Brand NewItem Type: Intercom Relay BoxMaterial: Aluminum Alloy Description: Simple operation, no power is required, no replacement of any part of the intercom is required, all you need is two hand‑held interphones and connect the cable to the external micron/SPK ports ( 2.5mm and 3.5mm). Using two hand-held walkie-talkie headphone jacks is composed of a very practical small relay station via a relay box.Single Cable Length: Approx. 50cm / 19.7inColor: Black Connector: Has the same connector as the K port on most radiosRepeater increases call distance over 10km, two-way communication (receiving and transmission)Installation: Two hand-held two-way walkie-talkies are connected to the repeater via a headphone plug