Features: brand new and high quality This walkie talkie in open call distance can reach 5-8 for km, it can long-distance communication. The operation is very simple, and no power supply needed, You do not need to change any part of the radio, All you need is just two handheld radios and connect the cables to the external mic/spk ports (2.5mm and 3.5mm). Using two handheld walkie talkie headset jack is composed of a very practical small relay station through the relay box. The scope of application:The link between the relay station and relay stationRelay station signal coverage area of signal extensionThe field construction of cable erectionUnderground mineCave constructionCulvert emergency rescueV-U for cross section relaySmall basement and ground walkie talkie signal connectionLarge activities and other occasions emergency use. The one-way relay box forwarding mode (conventional relay station mode). A machine receives the signal, the B machine transmission signal. Sending / receiving machine must be set to two different frequencies, the frequency is higher than the conventional transmitter set receiver frequency, and high / lower, high / low frequency difference of the 10M, the frequency difference is bigger is better. Package Includes: 1 Set RC-108 Repeater Box Specifications: Material:Plastic Color:Black Size:Approx.18x16x2cm/7.09x6.3x0.79inches note: 1.Please allow 1-2cm errors due to manual measurement, make sure that you do not mind before you order. 2.Due to the difference between different monitors, the picture may not reflect the actual color of the item.