Method and apparatus for providing answer supervision and an autonomous pay telephone incorporating the same

Claim 1

An arrangement for connection to a mobile full duplex radio including handset means for placing and receiving a telephone call and transceiver means coupled to said handset means via a communicaiton line for transceiver calls placed and received by said handset means, for providing a mobile autonomous pay telephone, comprising: a memory for storing charge information including at least outgoing call rate information for setting a rate to be charged, per unit of time, for an outgoing call to a given telephone number; charging determining means coupled to said communication line for receiving the telephone given number and for determining a charge for the call based on at least the rate to be charged for the outgoing call placed to the given number from at least the outgoing call rate information stored in the memory; metering means for accessing, in real-time, as a call progresses, the charge for the call as determined by the charge determining means utilizing at least the outgoing call rate information; display means for displaying, in real-time as the call progresses, charges accessed by the metering means for the call placed to the given telephone number; call answer supervision means for determining when a call has been answered by a called party; said call answer supervision means comprising: tone generating means for transmitting a tone of a given frequency on a transmit line of a mobile full duplex radio; tone detection means for monitoring a receive line of a mobile full duplex radio and the determining if the tone is received back on the receive line; audio activity detection means for simultaneously monitoring the transmit and receive lines for the presence of audio activity; cadence determining means for determining if the audio activity, present on at least one of the transmit and receive lines, has a repetitive cadence; and answer confirmation means for determining that the placed call has been answered if at least one of the following conditions occurs; 1) the tone of the given frequency is detected as received back on the receive line by the tone detecting means; and 2) audio activity having an irregular pattern is detected both on the transmit and receive lines of a mobile full duplex radio by the cadence determining means.