[AMRadio] Numbers Stations - NPRs slant

Robert M. Bratcher Jr. bratcher at pdq.net
Sat Nov 13 21:35:39 EST 2004

At 11:26 AM 11/13/2004, you wrote:
>acohen at texas.net writes:
> > I also had a friend who discovered that old pay telephones used to use
> > the sound of the falling coins striking a bell to determine whether the
> > money was properly deposited in the phone.
>Payphones later used frequency-shifted DTMF tones to signal the deposit of
>each coin.  I changed the crystal in an accoustic speed dialer to make 
>that set
>of tones...

Yes thats a red box...

>  worked quite well until they rigged the phones to mute the mic
>until money was deposited.

All COCOT phones. Local telephone company phones I'm not sure....

>  And now it is all done as digital signaling out of
>the voice-frequency range.

Which is why the blue box stopped working.

>Steve WD8DAS

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