not sure about the encoders.. they are either quadrature or just the sensor output. (wave shaping done in the electronics that we don't have)
I have a Puma 560. The early ones (including mine) have sin/cos encoders. They are optical and produce 1.8v p/p if I remember correctly. I added incremental encoders to mine for ease of interface. They also have a pot on each motor which is geared to match the complete travel of the joint. This gives a rough 'absolute' position for the calibration process. Motors are rated at 48V DC with 24V brakes.