Support is limited to customers who have already adopted these products. The PS2501-1, -4 and PS2501L-1, -4 are optically coupled isolators containing a GaAs light emitting diode and an NPN silicon phototransistor. The PS2501-1, -4 are in a plastic DIP (Dual In-line Package) and the PS2501L-1, -4 are lead bending type (Gullwing) for surface mount.