[Larry R]

Thank you for the suggestion! I see in the Honeywell spec sheet that the output is "sink" - no doubt open collector. I sure missed that. Following your suggestion, I used a 4.7K pull-up resistor and also tried using +5v and it works great. I get the low going (from about +5v to gnd) pulses at about 20 mS in width. I like that output! Instead of uS spikes, I see pulses with mS duration. I think this will be easier to work with.

I will look forward to the pictures. After seeing the form factor of these GTS, I know for sure they will not be mounted in the gear boxes.

To be sure I understand your post, you connected the pulled up output to any digital I/O pin on the robot controller and ran the GTS off the +5v supplied by the controller. Right? And the software you are using to count gear teeth has been pretty much posted - am I right about that also? I gathered a lot of programming info following your links on other posts.

This brings up my final question. From looking at the software, it seemed to me that due to the narrow uS spikes that the KOP gear tooth sensor outputs, you employed an interrupt-driven approach: " In the RC we used interrupts 2 and 3 (on RC DIO pins 1 and 2). Every time the gear tooth stimulates a low-to-high transition on the signal pin, an interrupt is thrown. "

I note that you referred to a low to high transition generating an interrupt. However the Honeywell units make a high to low. I am assuming the interrupt is edge sensitive and not level sensitive. Am I right about this?

Thanks a million for all your help!
Cheers, Larry