Even in the 1980's this may be a hall-effect sensor. Is the rest of the electronics still functional? You may find that it is supplied with a constant 5V. Put 5V on those pins yourself and then measure the output voltage.
Even in the 1980's this may be a hall-effect sensor. Is the rest of the electronics still functional? You may find that it is supplied with a constant 5V. Put 5V on those pins yourself and then measure the output voltage.