Just wondering if anyone as any info on what Tag Heuer HL 558 are used for. I found them in a box in our race room. They appear to be some kind of opto-isolater.
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Do you mean an HL-553? It's an opto-coupler and impulse distributor. They are useful for filtering false impulses on noisy timing wires.
No they are 558's. I have used the hl-553 many times. I added a photo here and an album in the General thread.
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I have one, called an impulse conditioner. Not sure about the technical aspects of how the electronics work but basically the same desired result as an optocoupler. We got one about 15 years ago and used it to help prevent false finishes caused by induction from power lines to a lift that ran under the finish area. I still have it but have not used it in years.
I figured that is what it was. Thought it was odd that I couldn't find anything on the internet about them. I used them for a couple of high school races and they seemed to work fine. The knob on the front seems to be some kind of delay except that instead of blocking any impulses for that period of time it sends one long impulses for that time.