Transmit/receive arbitrator
The amplitudes of a signal on the microphone input of a telephone and a signal on the line input of the telephone are compared with each other and with two thresholds. The comparisons are sampled and the samples control an up-down counter. The count in the counter is compared with two thresholds and the results of the comparisons are used to control at least two accumulators. A first accumulator counts consecutive comparisons having the same result and a second accumulator counts up or down in accordance with the comparisons. The counts in the first and second accumulators are logically analyzed to determine whether to receive or transmit. A plurality of samples defines a window, at the end of which the up-down counter is reset. The accumulators store data from a plurality of windows.
1. In a speakerphone having a line input and a microphone input, a method for comparing a first signal on the microphone input with a second signal on the line input to determine whether to transmit or receive, said method comprising the steps of:
(a) comparing the signals to each other and to at least one threshold to produce a binary representation of the comparisons;
(b) converting a plurality of binary representations into a first count; and
(c) comparing the first count to at least one count threshold to indicate whether to transmit or receive.
2. The method as set forth in claim 1 wherein comparing step (a) includes the steps of:
comparing the signals in an analog comparator;
sampling the output of the comparator to produce said binary representation of the comparison.
3. The method as set forth in claim 1 wherein comparing step (c) includes the step of (d) providing a binary indication of the results of comparing the first count to at least one count threshold.
4. The method as set forth in claim 3 and further including the step of:
(e) controlling a first accumulator and a second accumulator with said binary indication;
wherein the first accumulator counts consecutive binary indications of the same value; and
the second accumulator increments or decrements in accordance with the binary indication.
5. The method as set forth in claim 4 and further including the step of:
(f) logically comparing the counts in the accumulators to produce a binary signal.
6. The method as set forth in claim 5 wherein step (f) includes the steps of:
comparing the count in the first accumulator to a threshold and producing a first single bit representation of the comparison;
comparing the count in the second accumulator to a threshold and producing a second single bit representation of the comparison;
logically combining the first bit representation with the second bit representation.
7. The method as set forth in claim 1 wherein said comparing step includes comparing the first signal to a first threshold and comparing the second signal to a second threshold.