Plantronics Supra SHS1585-01NC 992C Headset

©Brooke Clarke, N6GCE

New military communications headset w/6-pin audio connector. Plantronics Supra Kit model SHS1585-01NC 992C has boom mic and hand PTT switch. Comes in box with instructions. from American-Milspec.

Photos from American-Milspec. Scan -

This headset has a simulates carbon mike and needs DC bias for operation.
It will need a wiring modification to work with the 5-pin mil radios.
The factory wiring is as follows:

Connector pin A, Black wire in headset cable = Microphone Common
Connector pin B, Red wire in headset cable = Microphone High
Connector pin C, Yellow wire in headset cable = Speaker
Connector pin D, Green wire in headset cable = Speaker
Connector Pin E, Blue Wire in headset cable = PTT Switch
Connector Pin F, White wire in headset cable = PTT Switch

Conversion for Mil Radios

It turns out that this headset was made to replace a carbon mike unit, but is uses some other kind of mike and active circuits for both the mike and earphones.
The power for the circuits comes from the DC bias that the equipment supplied for the carbon mike. The polarity does not matter since there is a diode bridge in series with the DC power line. It wants to see about 10 mA. This can be provided from a standard 9 Volt battery and a 680 Ohm resistor. The top from a dead 9 Volt battery can be removed and used as a snap connector. These are connected in series between the outside black and red wires which are bridged across the black and red mike wires going to the headset. A rubber band to hold a pair of pliers closed makes a "third hand".
Rewire the connector as follows:

radio Ground - A = Black (mike com), Green (speaker), White (PTT) + black wire to outside
radio Ear - B = Yellow (speaker) + 1 K Ohm resistor to pin A (this is to mute the radio's internal speaker)

radio PTT C = Blue PTT
radio mike D = Red (mike) + red wire to outside

As an aside the customer service from Plantronics has been first rate. This is a very high quality company. They also warned me that this model is obsolete.

The above conversion does not work as well as it should. Someone said that the grounds may need to be done differently?

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