Headset sources
rcrowley.com
Intercom Clone
Headset Sources
Any modern (or military surplus, for that matter) headset can be used in this circuit. The output level and drive current will drive most any earphones to a usable level.
I have a couple of military surplus aircraft headsets which have a noise-cancelling microphone (dynamic). These work just fine, but you must have the microphone right up against your lips. This is the nature of noise-cancelling microphones.
You can also use electret microphones with the addition of a component. To provide the power to the electret mic, add a resistor from the VCC/2 source (because it is well filtered and the voltage is plenty). Connect the other end to the junction of JP4, C10, R13, C23.
We used Koss SB-30 headsets for most of the intercom units. They are a little lightweight for use on the road where you have volunteers with no experience using the equipment and unpacking and packing it. We have seen some of the microphone goosenecks break, and some of the headbands break at the angle just above the earphone yoke.
Koss sells both double-side and single-side units, although the single-side unit is not shown on their website.
Koss Online Catalog Most any of the headsets listed in the "Communications" section would be usable with this circuit. There are several different kinds to meet different needs.
