...Antenna sockets on the backs of TVs are a really good place to get hit with this 
...
...in close proximity to 25-50 subscriber lines, any one of which might get an incoming call....90VAC doesn't exactly tickle.
@Fred: Just as a matter of interest, do you have an RCD, (safety switch), installed ?
-4wd
Maybe a bit off-topic but following on from what you said:
(a) TV antenna feeds: Yes, I have been zapped by domestic TV antenna feeds - the shock came off the outer (Earth) shield of the 75ohm (?) coax cable. If it happens, I always earth them (in the junction box) to mains Earth, because the shock could harm a toddler, even if not an adult. It's enough to hurt and make the spark jump a gap (same as the USB spark in the opening post).
(b) Telephone lines: Yes, you need to take care with those. Playing around with modems can give you a healthy respect for the voltages/currents involved. When a ringing signal is being sent there is an AC voltage pulse superimposed on top of the normal DC voltage. This AC "ringing voltage" pulse would nominally be around 90vAC at at a freq of 20Hz, but could peak at around 130vAC at different frequencies.
The potential difference (voltage) across the tip and ring wires is usually around 50vDC when the telephone is not being used (i.e., is "on hook"), and this drops to drops to around 6vDC when it is in use (i.e., is "off hook").
These voltages could be quite handy! I recall seeing one early example of a nifty and compact digital phone with several memories (presumably a hot new feature at the time it was designed) that seemed to have no independent power supply of its own, and was completely parasitic off the phoneline's DC supply. It worked very well too. I think it's illegal to attach such parasitic phones to the PSTN now though.
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