Abstract: A touch-tone receiver (TTR) simulator is disclosed to analyze DTMF signals and facilitate the investigation of call failure problems. The TTR simulator captures DTMF data received by a private branch exchange (PBX) switch and utilizes the instruction set of the TTR being simulated to process the received DTMF signals on the simulated TTR. Diagnostic tools allow step-by-step tracing and recording of the instructions performed by the simulator. The TTR simulator allows the underlying cause of a call failure problem due to DTMF signals to be identified. Results of digit interpretation can be compared to expected results.

Abstract: A method for processing telecommunications signals to alleviate echo during a voice communication between a local talker and a remote talker comprises the application of circular buffers for near and far end signals to preserve processing time. Overlapping blocks of samples are processed and indexed by incrementing the index over time to generate an array for storing magnitude coherence versus time delay between outgoing and incoming samples. Echo is clipped based on power spectral matching. The clipped echo is replaced with noise fill of at least one of two types, white noise and tonal noise, at an appropriate level. Also, crackle which comprises high energy spikes and a residual echo effect which is low energy, bursty and non-linear may be identified and replaced with noise fill.