31 Dec
2005
31 Dec
'05
7:40 p.m.
der Mouse wrote:
I don't think
curiosity is worth risking breaking the one really good DTMF phone I
have, so I can't trace my circuit to tell how well it matches your
schematic.
Well, I was curious: here's the schematic of my 'main' phone, an
Automatic Electric touch-tone from 1969.
... makes a little more sense than the Bell schematic.
http://www3.telus.net/~bhilpert/tmp/touchTone1969.gif
You can see the one transistor formed into an oscillator
with two resonant circuits. I too was rather surprised/amused
at it's simplicity when I RE'd it.
