An electrical device such as this requires reverse leakage current of 5μA @ 27.4V.During operation, the maximum voltage - Zener (Nom) is reduced to 36V volts.
1N974B_T50A Features
reverse leakage current of 5μA @ 27.4V 5μA @ 27.4V is the maximum voltage (Tol)
1N974B_T50A Applications
There are a lot of ON Semiconductor 1N974B_T50A applications of zener single diodes.