Browse Prior Art Database

Digital Tone Generator

IP.com Disclosure Number: IPCOM000061485D
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Cukier, M: AUTHOR

Abstract

The modems are provided with an alarm device which sends a side band tone when there is a power failure. Such a device is generally an analog block with a capacitor tank loaded by DC voltage and providing the required energy for disconnecting the regular power supply from the oscillator, connecting the oscillator to the capacitor and sending the alarm tone over the line for 100 milliseconds (ms). Such an analog implementation has several drawbacks, mainly the noise generation caused by the harmonics of the tone because the oscillator is always running. The proposed approach is based on the fact that, after a power loss, the DC voltage remains within voltage specifications for at least 200 ms, and therefore can provide the energy needed to send the tone. In after a predetermined delay, e.g.

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Digital Tone Generator

The modems are provided with an alarm device which sends a side band tone when there is a power failure. Such a device is generally an analog block with a capacitor tank loaded by DC voltage and providing the required energy for disconnecting the regular power supply from the oscillator, connecting the oscillator to the capacitor and sending the alarm tone over the line for 100 milliseconds (ms). Such an analog implementation has several drawbacks, mainly the noise generation caused by the harmonics of the tone because the oscillator is always running. The proposed approach is based on the fact that, after a power loss, the DC voltage remains within voltage specifications for at least 200 ms, and therefore can provide the energy needed to send the tone. In after a predetermined delay, e.g., 40 ms, no transition has been detected by the Transition Detector, the Tone Length Control is made active and sets an AND circuit for the time interval of 100 ms during which a tone has to be transmitted. The tone is generated by a Sine Generator consisting of a parallel register of 8 bits and a Decoder. The Decoder is built from the truth table providing the 8-bit words the value of which is the amplitude of the sine-wave signal generated each time a word is outputted. For instance, such a Sine Generator can be a modulo 30 counter providing 30 different words. With an input clock of 9600 Hz, it generates a 320 Hz sinewave signal.

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