Roman, I did not consider that you would have to resolve single detents.
You are right about there being one detent where there are two (-) pulses.
I propose the following two solutions:

1. Use a Schmitt trigger on each input. The Schmitts will 'integrate' the
pularised pulses and produce normal quardature outputs (sin,cos, indigital
form). The Shmitt can be implemented with the opamps I suggested.

Try these values: 10K/10K and decouple to gnd with 1uF for reference,
connect motor common here.

Each trigger has - input to referencee, 1K from (+) input to motor phase,
1M positive feedback from out to (+) input and 4k7 pullup on the output.
The 1M may have to be reduced to up to 100k to improve noise immunity.

2. Build two fliflops using IIL technology with a few discrete
transistors, each controlled by a motor phase. IIL has low logic levels
and it should work with the motor voltages properly.

Peter

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