From the Avon Lady's OFP FAQ:
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How can I communicate with other players during an MP game?
If you've got OFP: Resistance and are using OFP's new socket MP interface to connect to OFP servers, you'll need to use an external program for voice communications during MP gameplay.
For all older versions of OFP and for those continuing to use OFP: Resistance with the DirectPlay MP interface, you'll most probably be satisfied with OFP's own built-in Voice-Over-Network (VON) and text communication facilities.
Before you can use OFP's VON, you'll have to make sure that OFP can work correctly with your computer's microphone. To do this, run the OFP preferences program and click on the VOICE SETUP button. This will run a sound wizard test program. Follow the instructions carefully and, when completed, you should be all ready for VON communications.
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