I am developing a voice program, and the problem is that AT#VRX & AT#VTX are only commands i know for recording and playing, I am using handset as listen and speak device. Now my problem is how to receive and transmit simultaneously (as in normal phones) I know that modems do operate in full duplex modes and AT#VLS=6 put modem in speaker phone mode. but when i switch in that mode nothing happened i.e the voice which i m playing in AT#VLS=2 didnt paly and also nothing is recorded. Please do reply if you know something about it. I am using a USRobotics Sportster 33.6 Voice Modem.