The Telex BTR-800 is a 2-channel, frequency-agile UHF wireless intercom Base Station, with channel access from each of four full-duplex beltpacks, stage announce output with relay closure, wireless talk around (ISO), the patented Enhanced ClearScan channel search feature, and a talk/listen headset station at the base.
 
https://www.bhphotovideo.com/c/product/334875-REG/Telex_71305A2_BTR_800_2_Channel_UHF.html