> But this one goes one step further. You have a screen
> with currency on it and when you hit a say...quarter,
> it would make the tones necessary to refund a
> quarter...there's nickel, dime and dollar as well!
> Plus there is straight DTMF, and BLUE box tones.
> It's a lot of fun to play with...just wish it still
> worked on today's phone systems!
It will probably work. Somehow a public phone has to communicat with central
how much money has to be charged/refunded, depending on the current rates.
Therefore the tone dialling has extra frequencies which aren't accessible
from keys but can, of course be created with any simple synthesizer chip by
superimposing of two sinewaves. I've just put it on my Newton page :-)
http://slsbd.psi.ch/~mmailand/Npages/DTMF/dtmf.html
By combining some of the 1633Hz column codes a sort of shift mode could be
entered to allow communication with the normally thumb phone. Maybe
frequency override is just a sort of shift level for the phone kbd.
-- With best regards / Viele GruesseMarco Mailand http://slsbd.psi.ch/timing
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