Circa Telecom 4B3S-75 Solid State 75V Fuse for Digital Lines (w/ self resetting current limiter)

Reference#: 68068
Item#: CR-4B3S-75


The 4B3S-75 series of 5 pin protector modules are designed for superior transient and power fault protection of most secondary 'off-hook' applications. The 4B3S-75 series also features PTC (positive temperature coefficient) technology. These optional self-resetting current limiters provide effective protection from 'sneak current' faults. The PTC is vastly superior to the competition’s heat coil solution, which requires that the module be replaced after each 'sneak current' event.

What is differences between Digital (Solid State) and Analog (Gas)?

Digital (solid state) offers a quicker response time for special equipment such as PBX systems. Analog (gas tube) offers a higher current handling capability, however the response time is slower. (Normally used with voice lines)

Digital (solid state) protection is preferred over analog (gas tube) protection for EVERY application, EXCEPT for CAT5 / CAT5e. ALL T1, E1, xDSL (ADSL, HDSL, VDSL) lines are CAT3. Gas tubes are marketed as more robust than digital (solid state). Gas tubes will handle extremely high current surges (10,000 A) for 10 applications. Solid state devices will function once at this current, and then fuse to ground to minimize equipment damage. This level of current represents a direct or almost direct lightning strike. With a lightning strike of this nature, it is still better to have the faster reaction time of a solid state device, and replace a inexpensive module versus expensive line equipment.


- Nanosecond response time
- Longer life span than conventional gas tube and
- External fail safe mechanism that permanently carbon arrestors grounds the module under sustained high current conditions
- Reduced 'pass through' of dangerous transients
- Integrated Test Points
- Fewer service calls
- UL & cUL listed
- Documented safe performance
- Designed to meet or exceed Telcordia standards