This part is a kind of semiconductor called 2N4443.

Function of this product has SILICON CONTROLLED RECTIFIERS.

Manufacturers : Digitron Semiconductors

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2N4441-2N4444 High-reliability discrete products and engineering services since 1977 SILICON CONTROLLED RECTIFIERS FEATURES  Available as “HR” (high reliability) screened per MIL-PRF-19500, JANTX level. Add “HR” suffix to base part number.  Available as non-RoHS (Sn/Pb plating), standard, and as RoHS by adding “-PBF” suffix. MAXIMUM RATINGS Rating Symbol Value Unit Peak repetitive forward and reverse blocking voltage(1) 2N4441 2N4442 2N4443 2N4444 VRRM, VDRM 50 200 Volts 400 600 Non repetitive peak reverse blocking voltage (t = 5ms (max.) duration) 2N4441 2N4442 2N4443 2N4444 VRSM 75 300 Volts 500 700 Forward current RMS (all conduction angles) IT(RMS) 8 Amps Average on state current, TC = 73°C IT(AV) 5.1 Amps Peak non-repetitive surge current (1/2 [ ... ]

2N4443 PDF Datasheet Download