Duplex transducer for simultaneous voice broadcast and reception

A duplex communications apparatus comprising:

• speaker means for receiving and responding to incoming audio signals from a source thereof for producing corresponding speaker sounds;
• first and second microphone means each operable for receiving and responding to said speaker sounds and to other sounds from outside said apparatus for producing respectively corresponding audio signals;
• means for positioning said first and second microphone means so that the audio signals representative of said speaker sounds of said first microphone means relative to the audio signals representative of said speaker sounds of said second microphone means present a ratio;
• amplifier means coupled with first and second microphone means for receiving and amplifying said audio signals according to respective first and second gains for producing respectively corresponding first amplified signals including first amplified speaker sounds signals and first amplified other sounds signals, and second amplified signals including second amplified speaker sounds signals and second amplified other sounds signals,
• said amplifier means including means for providing said gains so that said second gain relative to said first gain presents said ratio so that said first and second amplified speaker sounds signals are substantially equal and thereby present a common speaker mode between said first and second amplified signals;
• and
• means for receiving and responding to said first and second amplified signals for rejecting any common mode therebetween in order to produce output signals substantially free of said common speaker mode and thereby representative of said other sounds.