🚀 go-pugleaf

Hi All,

I'm trying to put together some cheap special effects for a Haunted House
and I'd like some advice.  I want to build a device that takes one audio
channel from a typical jam box and use it to control relays (the other
channel will be going to a speaker).

I have considered using DTMF or an old 300 baud Modem, but I'd have to
experiment with either of these before I had a working system (and time
is short).  I'm hoping that some of you have done this before and can
give me pointers.

Additional info:
 Tape: Stereo Endless Loop (30, 40, or 60 sec)
 Recording Deck:  Stereo deck with Line-in or Mic-in.
 Playback Deck:   Portable stereo with Amplified Speaker outputs only
 Control Channels: 2 binary, none analog... more would be better.
 Budget: Minimal (Less than $100, more like $25)
 Time: must be done by 10/22/92

As for DTMF, I've got a box that produces DTMF tones to a line level
output, so the easy half is taken care of - I've never used a DTMF
decoder chip, so I'm not sure how level sensitive they are, etc... 
Also, hooking the speaker output to a decoder chip will require some
attenuation and perhaps filtering.  The advantage of DTMF is that it
gives me 4 bits of data without extra components.

As for Modem, I've got a Radio Shack DC-1 (0-600 baud Direct Connect).
I know the modem works, but I'm not sure how to convert the DAA to line
level for recording. As for playback, I could most likely couple the
modem and the stereo through a 8:500 ohm audio transformer.  With the
modem, I only get 1 bit of info unless I add shift logic, in which case
I trade sample rate for channels, though I could get hundreds of channels
before this becomes a problem.

Any suggestions or chip recommendations would be appreciated.

-Dean Reece (deanr@sco.com)