Margaret A Poole

US Patent:

39366111, Feb 3, 1976

Filed:

Sep 4, 1974

Appl. No.:

5/502933

Inventors:

Margaret A. Poole - Wayland MA

Assignee:

GTE Sylvania Incorporated - Stamford CT

International Classification:

H04B 166

US Classification:

179 1555T

Abstract:

Time compression scanner for monitoring telephone lines to detect supervisory tones. Eighty-eight lines are organized into eight groups of 11 lines each. The corresponding lines of each group are sampled simultaneously by a first arrangement of eight multiplexers. A second multiplexer repeatedly samples the eight samples from the first multiplexers. These analog samples are converted to digital samples and stored in a digital memory. The memory stores a set of samples pertaining to the incoming signals present on one line of each of the groups. When the first multiplexers each switch to the next line of each of the groups, the stored digital samples are read out of the memory. The samples are read out of the memory for each group in order, converted to analog signals, and passed through a low pass filter. The frequencies present in the resulting signal are speeded up by a factor of eight over the frequencies of any supervisory tones present in the incoming signal from which it was derived. These signal frequencies are passed through reject filters, comparator and limiter circuits, a bank of tone filters, and level detectors to check for each possible resultant frequency and to produce an indication of the presence or absence of each.

US Patent:

39314804, Jan 6, 1976

Filed:

Sep 4, 1974

Appl. No.:

5/502939

Inventors:

Margaret A. Poole - Wayland MA

Assignee:

GTE Sylvania Incorporated - Stamford CT

International Classification:

H04M 150

US Classification:

179 84VF

Abstract:

Time compression receiver for detecting the signalling tones in a DTMF (dual tone multi-frequency) format present on eight receiver input lines. A multiplexer repeatedly samples the input signals present on the eight input lines. These analog samples are converted to digital samples and stored in a memory. Stored samples are read out for each input line in order while new samples are being written into the memory. Samples are read out at twice the rate they are written in. The samples are converted to analog signals and passed through a low pass filter. The frequencies present in the resulting signal are speeded up by a factor of sixteen over the frequencies of the signalling tones present in the input signal from which it was derived. The signal frequencies are passed through reject filters, comparator and limiter circuits, a bank of tone filters, and level detectors to check for each possible resulting frequency and to produce an indication of the presence or absence of each.