4 ms·
The cable TV shield is grounded where it enters the house. The POTS lines aren't grounded (they're differential, like 1000base-T), but the telephone company in
by fleventynine 3y ago
The cable TV shield is grounded where it enters the house. The POTS lines aren't grounded (they're differential, like 1000base-T), but the telephone company installs some sort of protection device in the exterior box that allows sparks to jump across to the local ground if the voltage differential gets too high.