.The Poly (formerly Plantronics) Y-training 3.5mm cable part # Poly 217008-01 or HP 85S08AA can be connected inline of specific corded headset models for being able to connect a second headset for training/monitoring purposes. The 3.5mm y-training cable connects two Blackwire 5200 USB headsets to the USB port and monitors or trains. Both users can hear the conversation, but only one headset (red end on the Y-cord) has the microphone turned on. The microphone of the other headset (supervisor/trainer) is always muted.