YS-138LK-S is the same as YS-138LK. The difference is that YS-138LK-S has signal output. YS-138LK-s is a Long Type European Electric Strike. Which is made of Stainless Steel. The Holding Force is 500KG. The Voltage is default DC12V.
Electric strikes come in many varieties.YS-132NO/NC-S is the electric strike with long faceplate and signal output. It has two modes: A fail safe electric strike needs power to keep it locked. A fail secure electric strike stays locked.
YS-621-S is suitable for fire exit door with Push-rod lock.The operating principle of electric strike is that electromagnetism produces the force to pull or push the release lever so that to lock or open the door.