This part is a kind of semiconductor called B59603B.

Function of this product has (B59xxx) Line Card Applications.

Manufacturers : EPCOS

Image and pinout :

Some of the text within the PDF file :

Telecom Line Card Applications, Leaded Disks Applications I Overcurrent protection for line cards B59*** B 10**, B 11**, B 16**, C 10** Features I Compliant with ITU-T K20, K21, K45 – basic level lightning surges (10/700 µs) – basic level power induction (600 V, 1 A, 0,2 s) – power contact criteria A/B (230 V, 15 min.) I Suitable for continous connection to mains voltages of 110/230 VAC in tripped (high ohmic) condition I Narrow resistance tolerance Options I Alternative tolerances and resistances on request Delivery mode I Cardboard tape, reeled (standard) or in AMMO pack (on request); cardboard strips (on request) I Exception: B 1610, cardboard strips (standard), cardboard tape or AMMO pack on request Dimensional drawings Kinked leads b s Straight leads b [ ... ]

B59603B PDF Datasheet Download