Computer controlled speakerphone for adapting to a communication line

DETAILED DESCRIPTION FIG.
1 is a functional block representation of a computer controlled adaptive speakerphone 100 operative in accordance with the principles of the invention.
As shown, the speakerphone generally comprises a transmit section 200, a receive section 300, and a computer 110.
A microcomputer commercially available from Intel Corporation as Part No.
8051 may be used for computer 110 with the proper programming.
A microphone 111 couples audio signals to the speakerphone and a speaker 112 receives output audio signals from the speakerphone.
By way of operation through illustration, an audio signal provided by a person speaking into the microphone 111 is coupled into the transmit section 200 to a multiplexer 210.
In addition to being able to select the microphone speech signal as an input, the multiplexer 210 may also select calibration tones as its input.
These calibration tones are provided by a calibration circuit 113 and are used, in this instance, for calibration of the hardware circuitry in the transmit section 200.
Connected to the multiplexr 210 is a mute control 211 which mutes the transmit path in response to a control signal from the computer 110.
A high pass filter 212 connects to the mute control 211 to remove the room and low frequency background noise in the speech signal.
The output of the high pass filter 212 is coupled both to a programmable attenuator 213 and to an envelope detector 214.
In response to a control signal from the computer 110, the programmable attenuator 213 inserts loss in the speech signal in three and one half dB steps up to a total of sixteen steps, providing 56 dB of total loss.
This signal from the programmable attenuator 213 is coupled to a low pass filter 215 which removes any spikes that might have been generated by the switching occurring in the attenuator 213.
This filter also provides additional signal shaping to the signal before the signal is transmitted by the speakerphone over audio line 101 to a hybrid (not shown).
After passing through the envelope detector 214, the speech signal from the filter 212 is coupled to a logarithmic amplifier 216, which expands the dynamic range of the speakerphone to approximately 60 dB for following the envelope of the speech signal