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Parallel Tone Generator using Variable Period Counters

IP.com Disclosure Number: IPCOM000078989D
Original Publication Date: 1973-Apr-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Adams, RL: AUTHOR [+2]

Abstract

Digital techniques can be utilized to provide a multifrequency sinusoid generator (MFG) for telephone signalling purposes. This digital approach utilizes oscillator-driven counters and logical means to reset the counter circuitry periodically, in response to control inputs to the logical circuitry indicative of the desired output frequencies. The pulse output and filter circuits are responsive to the reset rate of the counter circuits, to yield the desired sinusoidal output signals.

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Parallel Tone Generator using Variable Period Counters

Digital techniques can be utilized to provide a multifrequency sinusoid generator (MFG) for telephone signalling purposes. This digital approach utilizes oscillator-driven counters and logical means to reset the counter circuitry periodically, in response to control inputs to the logical circuitry indicative of the desired output frequencies. The pulse output and filter circuits are responsive to the reset rate of the counter circuits, to yield the desired sinusoidal output signals.

In the figure, two counters 10, 12 are driven by a common oscillator source 14, and the respective outputs of the counters are decoded by circuits 16, 18. The various decoder outputs are energized at the counts shown on the drawing and the resulting signal is passed by an AND circuit from each of A and B banks 20, 22 in a selective manner, when corresponding A control signal and B control signals are provided to the other leg of the selected AND circuits. These control signals may come from telephone push button switches, not shown, in a conventional manner.

The outputs of the AND's are OR'd at 24, 26 and are operative to reset the corresponding counters 10, 12 via lines 26, 28 as well as to switch the corresponding binary trigger 30, 32. The AC outputs of 30, 32 are filtered at 34, 36 and summed at 38 to yield a conventional A,B MFG output. Counter 10 is used for generation of the A group frequency (697, 770, 852 and 941 hz) and ...