Telikou BK-101/4 is a single channel Electret button belt pack

PTT (push to talk) and Latching Microphone button
Call button; Call light; Volume control
Sidetone adjustment
XLR-3M and XLR-3F Loop-through Intercom connectors
XLR-4M headset connector
3.5mm headset connector

The BK-101 is compatible with TELEX and Clear-Com Party-Line intercoms