Resettable fuses are fit for telecomms protection

A new series of resettable fuses specifically designed to protect telecomms equipment against overcurrent and overvoltage conditions has been introduced by Wickmann Components.

A new series of resettable fuses specifically designed to protect telecomms equipment against overcurrent and overvoltage conditions has been introduced by Wickmann Components.

The Polyfuse HVR250 Series fuses are optimised to provide fully resettable overcurrent protection for equipment covered by the International Telecommunications Union's K20 and K21 standards.

K20 addresses central office switching equipment including line cards, modems, splitters and multiplexers, whereas K21 covers customer premises equipment including modems, fax machines, caller ID boxes, voice over IP appliances and PBX equipment.

Overvoltages, which are typically caused by lightning surges or AC power faults, are usually limited by using gas tube surge arresters or varistors.

However, this can produce high fault currents that can overload the protection components and overheat the tip and ring lines on the equipment's input, resulting in damaged components and failed equipment.

HVR250 fuses protect the equipment from induced current conditions and automatically reset on correction of the fault.

Resettability also has the added advantage of reducing the number of service calls.

The HVR 250 is available with hold currents from 80 to 180mA.

Rated operating voltage is 60V and maximum interrupt voltage is 250V to comply with the AC power crosstests.

The fuses can be supplied either bulk packaged or taped for auto-insertion.

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