>sorry, I could not resist this.
>
>Peter
>
>

It's a very good contribution, actually.  It proves that such devices can
be constructed.  I'd imagine that 20 meters is quite a long ways in a game
of laser tag.  I was playing around with a laser diode I've got here, and I
managed to transmit a signal about 300 yards down the street to a pickup,
and reflected it back off of a shaving mirror (it's true!).  The modulator
I used is available commercially (I know, since I bought it about 5 years
ago), but I don't recall who made it.  I'll have to research a bit.

However, the transmitter is about the size of a toilet paper tube, with a
collimating lens on the front (I get a one inch beam diameter out of this,
to make the target easier to acquire).  The receiver uses an off the shelf
IR detector, some crud inside to decode the pulses (I haven't torn it
apart, really!), a 1W audio amplifier and a 1/8 in. phono jack.  I added,
in front of the detector, a prismatic array off of a laser rangefinding
target (used in surveying).  That way, I can tell when I've hit the target.

I think the modulator runs at about 48kHz, and gives you something like
4000 bytes per second.  It's a great toy, but way to big (and it requires
an AC power supply) to use in a toy.

Ken