This part is a kind of semiconductor called 1N5251B.

Function of this product has Absolute Maximum Ratings.

Manufacturers : Fairchild Semiconductor

Image and pinout :

Some of the text within the PDF file :

Zeners (1N5221B - 1N5279B) Zeners 1N5221B - 1N5279B Absolute Maximum Ratings* Symbol PD TSTG TJ TA = 25°C unless otherwise noted Tolerance = 5% Parameter Power Dissipation Derate above 75°C Storage Temperature Range Maximum Junction Operating Temperature Lead Temperature (1/16” from case for 10 seconds) Value 500 4.0 -65 to +200 + 200 + 230 Units mW mW/°C °C °C °C *These ratings are limiting values above which the serviceability of the diode may be impaired. **Non-recurrent square wave PW= 8.3 ms, TA= 50 degrees C. NOTES: 1) These ratings are based on a maximum junction temperature of 200 degrees C. 2) These are steady state limits. The factory should be consulted on applications involving pulsed or low duty cycle operations. DO-35 Glass case COLOR BAND DENOTES CATHODE Elec [ ... ]

1N5251B PDF Datasheet Download