Long Range Certificate Course

In marine radio communication equipment fuses are quite often used. A fuse is a protection against too high a current. Fuses allow the passage of a normal current, but can interrupt a short circuit or an overloaded condition that could cause damage to the radio equipment.


Fuses are not all the same: we recognize "fast", "slow" and "time-delayed" fuses. A “fast” fuse will react immediately when the current is too high. A “slow” fuse will have a delayed reaction. A "time-delayed" fuse will react even more slowly.

On a fuse we can discover some marks, for example:

• F 5A/60V, this means that it is a “fast” fuse (F), maximum current 5A, maximum allowed voltage 60V
• S 100mA/250V, this means that it is a “slow” fuse (S), maximum current 100mA, maximum allowed voltage 250V
• T 400mA/250V, this means that it is a “time-delayed” (T) fuse, maximum current 400mA, maximum allowed voltage 250V
  

When a fuse is “blown out” we should try to find the reason that caused this problem before replacing the fuse. We should replace the fuse with a fuse of the same type and rating (value).

If we don't have a spare fuse of the same value, we can use one with a "lower" value" until we are able to replace it with the fuse of the same value. We should not use one with a "higher value" as the higher current may damage your equipment.

When the equipment needs a “fast” fuse this one should not be replaced by a “slow” one (of the same value), as in this case the short period of higher current may damage your radio equipment.

Replacing a “slow” fuse by a “fast” fuse (of the same value) will lead to an immediate blowing of your newly inserted fuse.