A near full duplex portable handset speakerphone comprises: a microprocessor;
a
hands-free receive register connected to the microprocessor; a hands-free transmit
register connected to the microprocessor; a ROM having a speakerphone operation
algorithm, the ROM connected to the microprocessor; a first analog-to-digital converter
connected to the hands-free receive register; a second analog-to-digital converter
connected to the hands-free transmit register; a first programmable digital attenuator
connected to the microprocessor and to a speaker; and a second programmable digital
attenuator connected to the microprocessor and to a microphone, wherein near full
duplex communication is achieved without digital signal processing. In another
feature of the invention, the hands-free registers provide a digital representation
of the speech volume in each direction to the microprocessor. The microprocessor
monitors the speech signal levels, calculates digital volume comparisons in order
to make speech gain decisions for optimal sound, and digitally adjusts the gains
in the two speech paths to the upper half of their maximum values.