This part is a kind of semiconductor called B4S.

Function of this product has MINI SURFACE MOUNT GLASS PASSIVATED BRIDGE RECTIFIER.

Manufacturers : Bytes

Image and pinout :

Some of the text within the PDF file :

B1S THRU B8S MINI SURFACE MOUNT GLASS PASSIVATED BRIDGE RECTIFIER VOLTAGE RANGE 100 to 800 Volts CURRENT 0.5 Ampere FEATURES * Ideal for printed circuit board * Reliable low cost construction utilizing molded plastic technique * High surge current capability * Polarity: marked on body * Mounting position: Any * Weight: 1.0 grams SMDI/MB-S MAXIMUM RATINGS AND ELECTRICAL CHARACTERISTICS Rating 25 C ambient temperature uniess otherwies specified. Single phase half wave, 60Hz, resistive or inductive load. For capacitive load, derate current by 20%. TYPE NUMBER Maximum Recurrent Peak Reverse Voltage Maximum RMS Voltage Maximum DC Blocking Voltage Maximum Average Forward Rectified Current See Fig. 2 Peak Forward Surge Current, 8.3 ms single half sine-wave superimposed on rated load (JEDEC m [ ... ]

B4S PDF Datasheet Download