GKC Part #441 Model #305 Communications Amplifier with 25 Number Memory Dialer Radius 5mm / (1/8") input for

5mm / (1/8") input for a microphone for talkback

External power input jack for DC supply up to 12V

Cord has a 3 pin XLR male plug on one end and an RJ 11 telephone plug on the other end

but with more features

This headset can be used for the Models #300

GKC Part #441 Model #305 Communications Amplifier with 25 Number Memory Dialer Radius 5mm / (1/8") input forThis advanced communications amplifier is most versatile for both IFB and ENG field operations. It operates similar to the Model 300 but with more features. It can be used on a standard telephone line, a satellite phone or IFB feeds, from a remote truck. The unit is used with a low impedance headset or a lapel mic and earphone. Features include two independent output channels, one for the headset output, the other for the IFB output with 1 4" and 1 8"