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Friday, 6 September 2013

Moments of my intimate contact with electricity:Telephone Line Voltage

I like wiring – since my childhood years – guess it is just the way i am.

One of my early experience as a teenager is to extend the telephone line – essentially i just strip the wires and twist the interconnect – with my bare hand. In the middle of doing that, muscle at my upper arm started twitching involuntary – it felt kind of funny – no pain but still… seeing part of your body behaving out of your control is kind of weird…

As it turns out, telephone line is typically at 40VDC, and when it rings it can go all the way up to 90VAC.. so i guess my twitching muscle act as the incoming call detector!! Smile


Having your body as part of current path is never a good idea, few mili ampere of current is enough to mess up your heart beat under the right condition – so give electricity some respect is what we should do..

Side notes:


IEC voltage range AC DC defining risk
High voltage (supply system) > 1000 Vrms > 1500 V electrical arcing
Low voltage (supply system) 50–1000 Vrms 120–1500 V electrical shock
Extra-low voltage (supply system) < 50 Vrms < 120 V low risk

< 120VDC is considered as low risk.

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