Wireless: DX-300 (MB300) Base Station Relay accessory connections
The Dx-300 (MB300) base station has two sets of relay connections that are accessible via the rear panel on a 8-pin Phoenix style terminal strip. They are labeled relay "O" and relay "X" and are associated with the O-channel and X-channel talk buttons on the BP300 beltpack and WH300 headset. Both relays can be accessed simultaneously by pressing the "ALL" talk button on the wireless beltpack or headset.
"O" and "X" relay wiring detail shown below: