This part is a kind of semiconductor called MPSA42.

Function of this product has EPITAXIAL PLANAR NPN TRANSISTOR.

Manufacturers : KEC

Image and pinout :

Some of the text within the PDF file :

SEMICONDUCTOR TECHNICAL DATA HIGH VOLTAGE APPLICATION. TELEPHONE APPLICATION. FEATURES ᴌComplementary to MPSA92/93. MAXIMUM RATING (Ta=25ᴱ) CHARACTERISTIC SYMBOL Collector-Base Voltage MPSA42 MPSA43 VCBO Collector-Emitter Voltage MPSA42 MPSA43 VCEO Emitter-Base Voltage Collector Current Emitter Current Collector Power Dissipation Junction Temperature Storage Temperature Range VEBO IC IE PC Tj Tstg RATING 300 200 300 200 6.0 500 -500 625 150 -55ᴕ150 UNIT V V V mA mA mW ᴱ ᴱ L M C MPSA42/43 EPITAXIAL PLANAR NPN TRANSISTOR BC JA K E G D H FF 1 23 N DIM MILLIMETERS A 4.70 MAX B 4.80 MAX C 3.70 MAX D 0.45 E 1.00 F 1.27 G 0.85 H 0.45 J 14.00 +_0.50 K 0.55 MAX L 2.30 M 0.45 MAX N 1.00 1. EMITTER 2. BASE 3. COLLECTOR TO-92 ELECTRICAL CHARACTERISTICS (Ta=25ᴱ) CHA [ ... ]

MPSA42 PDF Datasheet Download