The ENS1J-B28-L00128L is a self-contained rotary optical encoder manufactured by Bourns that produces a 2-bit quadrature signal with 128 cycles per revolution. It features square wave digital output signals that do not require debounce circuitry, with Channel A leading Channel B by 90° during clockwise rotation. The encoder operates at 5.0 VDC ±0.25 VDC with a maximum supply current of 26 mA, output voltage ranging from 0.8 V (low) to 4 V minimum (high), and rise/fall times of 0.200 ns typical. With a 7/8" long shaft (servo mount style W with ball bearing configuration), 1/4" diameter plain end, and axial multi-purpose pin termination, this encoder is ideal for digital panel controls and position sensing applications where long life, reliability, and precise linearity are critical. The device offers a useful rotational life of 10 to 200 million shaft revolutions, making it suitable for extended service applications in space-constrained environments.