SUPPLEMENTAL INSTRUCTIONS FOR SIGTRONICS HEADSETS

Information contained in the standard instructions is not repeated here, so read these in conjunction with the standard instructions.

1. Some Sigtronics models are wired in a different manner than the basic Dvid Clark ("D.C.") headset. If you study the color diagram provided (diagram showing green, red, & black circuits) you will see that in the standard David Clark headsets the audio+ (green) enters the left earcup, passes through the volume control, and then divides into two leads, audio R and L, one going to each speaker. In some Sigtronics models however (usually the stereo models) you will find that the audio (+) leads go directly to the speakers, and the ground circuit (-) passes through the volume control. To install the ANR Adapter modules in these models, the wiring must be altered slightly so that the audio (+) lead(s) pass through the volume control, as opposed to the ground (-) passing through the volume control.

2. The reason this arrangement will not work for the ANR module is because the modules use a common ground (for the audio and power system). If the volume control wee to remain on the ground circuit, the module would not be fully grounded. In short, the volume control may only be permitted to operate on the audio+ signal.

3. If you headset is wired like this, the audio (+) leads should be disconnected (desoldered) at the original speakers. The audio+ leads (R & L) can be identified because they are the leads that attach directly tot he speaker (an ohmmeter can be used to confirm and do not pass through the volume control. The audio+ (L) lad should be disconnected from the L speaker at this time. Also in the L earcup, the audio (-) R lad attaches to the crossover cable, & then passes overhead to provide audio to the right side, & should be disconnected from the crossover cable (in L earcup) at this time. Still in the L earcup, the two audio+ leads (R&L) should now be merged into one wire (making the headset mono) and that wire should now be attached to the volume control (soldered). After the audio (+) lead passes through the volume control, it should be divided into two leads, audio R & L, with one lad going to each side.

Note: when disconnecting wires from the volume control, don't disconnect any leads directly from the volume control terminals. Leave the original leads attached to the terminals & work with them "as is".

4. The only way to retain stereo is to add a 2nd volume control.

5. After disconnecting and rewiring as per above, the remainder of the wiring job is per the standard instructions, that is, the audio (-) ground and the 9v (-) ground join together to form a common ground, then divide into two leads, one "common ground" for each side.