More Conversion Tricks

by DC

The RadioShack Tone Dialer to Red Box conversion is the greatest example of a remarkable coincidence that I have ever come across.  The fact that the timing of the microprocessor inside the device and the tone pair for the DTMF asterisk when sped up creates a nearly perfect quarter tone sequence is beyond luck.  The entire conversion is poetry.  Thanks for the great work, Noah Clayton.

Being that the tone dialer itself is such a nice product (I believe it is, feature for feature, the best product RadioShack has to offer, considering most of what RadioShack has to offer sucks and is overpriced anyway) I didn't want to just convert mine into a Red Box.  I wanted to have the Red Box tones as well as the dialer capabilities.

Since reading the conversion article in the Autumn 1990 issue of 2600, I have come across a file explaining how to make the conversion but incorporating a switch to select between the two different frequency crystals, enabling both Touch-Tones and a Red Box.

One thing I didn't like about the file's design is that it had wires coming out of the back of the unit to the two crystals and the switch which were all epoxied together to the back of the unit.  Ugly.  I managed to fit everything neatly inside the unit.

The first thing I did was file the lip on the bottom of the 6.5536 MHz crystal flush with the rest of its case to give it a lower profile.  Looking at the circuit board with the battery compartment towards you.  I removed the screw on the upper-left-hand side near the two solder pads and diode and put the crystal in that area.  I also reduced the solder on the lower pad to make the slightest bit more room for the crystal.  I soldered one lead of the 6.5536 MHz crystal (extended with a piece of wire) to one lead of the 3.579545 MHz crystal.

I then soldered the other lead to the top leg of the SPDT switch and glued the crystal in place with some super glue.  I then desoldered the other leg of the 3.579545 MHz crystal and jumpered it to the bottom leg of the SPDT switch.

Finally, I soldered a jumper from the middle leg of the switch to the lead into the microprocessor (the lead that one leg of the 3.579545 MHz crystal was desoldered from).

I cut a slot in the side of the two halves of the case (the side opposite the ON/OFF and DIAL/STORE switches) and glued the switch in place.  It works like a charm.

The 6.5536 MHz crystal can also be ordered from RadioShack, by the way, for $4.95 each.  I wouldn't mention this if it weren't for the fact that Fry's Electronics wanted to charge me eight bucks shipping and handling alone on a cash order.

I also discovered that the tone dialer can be converted to generate the Green Box "coin return" tone.  Replacing the 3.579545 MHz crystal with one that has a value close to 4.1521 MHz (the calculated value) will cause the pound (#) key to generate frequencies close enough to the 1100 Hz and 1700 Hz Green Box tones (1091 Hz and 1713 Hz in actuality).

Making this mod to the dialer wouldn't suffice because you would still need a way to generate either 2600 Hz or 900 + 1500 Hz (the "operator release" signal) in order to send the Green Box tones.  If someone can figure out how to incorporate all needed Green Box tones into the dialer, I would like to hear about it.  It would be a nice complement to the Red Box.

Readers: Please send us your experiences and experiments to share.