Patent ID: 6172974
Filing Date: 2001-01-09
Classification: H04Q,H04W

Abstract:
In a voice communication system which includes an originating unit having a first vocoder, a first base station in wireless communication with and serving the originating unit, a first BSC/MSC having a vocoder in the first base station, a terminating unit having a second vocoder, a second base station in wireless communication with and serving the terminating unit, a second BSC/MSC having a vocoder in the second base station, the base stations being interconnectable via a voice channel, the units each containing an A/D-D/A converter, apparatus for achieving TFO of the system wherein the vocoders in both BSC/MSCs are bypassed, which apparatus comprises:signaling means in the second base station responsive to the receipt of a call initiation signal sent by the originating unit via the first BSC/MSC and the channel for sending a short duration, low frequency signal via the channel to the first base station, the frequency of the signal indicating the type and capabilities of the vocoder in the terminating unit and having a frequency which is significantly less than the rolloff frequency of the A/D-D/A converters;analyzing means in the first base station for analyzing the received low frequency signal and determining whether digital signals from the first vocoder are compatible with the second vocoder; andcontrol means in the base stations(a) for directing digital voice signals between the units around, and bypassing, both BSC/MSC vocoders in the base stations if the second vocoder is compatible with the digital signals from the first vocoder, and(b) for directing digital voice signals between the vocoders of the units through the BSC/MSC vocoders in a tandem mode if the second vocoder is not compatible with the digital signals from the first vocoder.