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The Alge PR1a has a sync port which is used to synchronize 2 units in transmit mode for primary and back-up timing. The Alge literature says that this minimizes "interference".

Can anyone tell me what that means? Interference where?

At first, I assumed that maybe the beam was actually pulsed and that this sybc'd the pulses. But if that's the case, the pulse period must be significantly less than 1/10,000 sec, which would make it insignificant.

If it is for interference prevention, then interference where? On the cable back to the timer?

Another question -- I've only seen reference to using the sync cable with through beam systems. We'll be using 2 reflector systems. I assume the same issues apply -- true?

Thanks for the help.

-- Mark
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The sync cable is ONLY used when there are two receivers and two transmitters set up in "FIS" finish line configuration.

Two reflector cell finish line do NOT use this cable.

The cable is only used on the transmit side and sets up an alternating pulse scheme so that the two cells do not interfere with each other.

There is a special cable (slightly different from iPod cable) that connects the transmitters. The small green led comes on when the beams are synced.

The cool thing about the PR1a is that all of the cells are the same. Each cell can either be a tx, rx or reflector cell.

Best racing photocell ever made.

That means that you can add just 2 more cells in the future at no penalty and create a through beam setup.

I too would love more detail. What is the exact nature and full detail of the “alternating pulse scheme”?  Like is it actually pulsing the infrared light from a given TX at like 200kHz or something, and with the sync cable it is actually interleaving the pulses of light so that A eye shines and stops shining , and then B eye shines and stops shining, and then A eye shines and stops shining etc etc etc.?   And how exactly would this help avoid interference?  If your RX’s are close enough to one another to see a pulse of infrared from a single TX eye, how do the RX’s know whose pulse it is?  Or do they have circuitry to know to expect the next pulse to be 1/200,000 of a s since the last one, and to ignore the one in between?  Ah, that must be it.  

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