The MC33215 is developed for use in fully electronic telephone sets with speakerphone functions. The circuit performs the ac and dc line termination, 2–4 wire conversion, line length AGC and DTMF transmission. The speakerphone part includes a half duplex controller with signal and noise monitoring, base microphone and loudspeaker amplifiers and an efficient supply. The circuit is designed to operate at low line currents down to 4.0 mA enabling parallel operation with a classical telephone set.

• Highly Integrated Cost Effective Solution
• Straightforward AC and DC Parameter Adjustments
• Efficient Supply for Loudspeaker Amplifier and Peripherals
• Stabilized Supply Point for Handset Microphone
• Stabilized Supply Point for Base Microphone
• Loudspeaker Amplifier can be Powered and Used Separately
• Smooth Switch–Over from Handset to Speakerphone Operation
• Adjustable Switching Depth for Handsfree Operation