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Posting-Version: version B 2.10.2 9/18/84; site wateng.UUCP
Path: utzoo!watmath!watvlsi!wateng!mjwingrove
From: mjwingrove@wateng.UUCP (Mike Wingrove)
Newsgroups: net.analog
Subject: sound synthesizing
Message-ID: <2930@wateng.UUCP>
Date: Thu, 6-Feb-86 15:31:30 EST
Article-I.D.: wateng.2930
Posted: Thu Feb  6 15:31:30 1986
Date-Received: Sun, 9-Feb-86 05:15:29 EST
Reply-To: mjwingrove@wateng.UUCP (Mike Wingrove)
Followup-To: mjwingrove@wateng.UUCP
Distribution: net.analog, net.micro
Organization: U of Waterloo, Ontario
Lines: 37
Keywords: phones, synthesizer
Summary: require generation of dial tone, ring back etc.


<**** We don't have a line eater ****>

I would be interested in obtaining some information about generating
sinusoidal waveforms under program control.  This would be for the 
purpose of simulating dial tone, ring back tone , busy signal etc 
on a telephone.

In particular I'm interested in what programmable chips if any have the 
following capabilities.

Must be able to generate frequencies up to about 1 KHz.

Should be able to resolve differences in frequency well (ie 5 or 10 hz steps).

Must have individually adjustable output levels on each of 2 voices.
(These need quite good resolution too, but I haven't calculated how much yet.)

Also does any one have any novel ideas as to generating the ringing voltage
(90 v rms ac 20 hz (20 ma I believe)) for the phone from a 24 volt (+,-12)
power supply. The current system uses a 20Hz Weinbridge oscillator driving
a class AB darlington output stage.  The output from the power stage then
drives a filament transformer (110 v primary 10 v secondary) in reverse to
step the voltage up.  This is a pig of a circuit (about 1/3 total board area).
Also it must be heavily bypassed to prevent the introduction of large
fluctuations on the +12,-12 voltage lines.  (The filament transformer is a
disgusting load to drive especially at 20 Hz.

Anyhow any suggestions would be welcome.

						Mike Wingrove
						Elec Eng Student
						Computer Communications
						Networks Group
						U of Waterloo

Disclaimer: I don't have any opinions!!!