R
Robert Scott
- Jan 1, 1970
- 0
In the recent ice storm, the 4800 volts from the power lines crossed over into
the phone lines. It burned out many circuits in our area. It also fried some
modems and phones in my house. Surprisingly, two connected modems survived.
These were both protected by whatever surge protection circuit they put in a
UPS. But it had the side effect of burning out that circuit in the UPS, so I
cannot use that again.
Rather than protect phone equipment piecemeal, I would like to protect all phone
equipement in my house using one circuit that I put at the entrance. I would
like to use a fuse. I gather that most commercial "surge protectors" do not
have fuses, but I think they might be a more reliable protection than varistors
or whatever they put in those commercial units. Has anyone done this? What
sort of current limit should I set? I guess the ringing with a maximum number
of phones connected would be the upper limit. But a fuse might not be enough.
What about a crowbar circuit? Is it possible to detect an overvoltage condition
with an active circuit and then short all lines to ground through some
fast-acting power FETs downstream of the fuses, just to make sure the fuses blow
right away? I don't mind replacing some power FETs and fuses in my own custom
circuit once in a while if it means I won't have to replace modems and phones.
I know ice storms and downed power lines are my focus right now, but I am also
looking toward spring with lightning will be the major risk.
Robert Scott
Ypsilanti, Michigan
the phone lines. It burned out many circuits in our area. It also fried some
modems and phones in my house. Surprisingly, two connected modems survived.
These were both protected by whatever surge protection circuit they put in a
UPS. But it had the side effect of burning out that circuit in the UPS, so I
cannot use that again.
Rather than protect phone equipment piecemeal, I would like to protect all phone
equipement in my house using one circuit that I put at the entrance. I would
like to use a fuse. I gather that most commercial "surge protectors" do not
have fuses, but I think they might be a more reliable protection than varistors
or whatever they put in those commercial units. Has anyone done this? What
sort of current limit should I set? I guess the ringing with a maximum number
of phones connected would be the upper limit. But a fuse might not be enough.
What about a crowbar circuit? Is it possible to detect an overvoltage condition
with an active circuit and then short all lines to ground through some
fast-acting power FETs downstream of the fuses, just to make sure the fuses blow
right away? I don't mind replacing some power FETs and fuses in my own custom
circuit once in a while if it means I won't have to replace modems and phones.
I know ice storms and downed power lines are my focus right now, but I am also
looking toward spring with lightning will be the major risk.
Robert Scott
Ypsilanti, Michigan