Can ayone tell me the speed at which signals travel through telephone wires?

Question

that would be the older copper wires for landlines and not newer fibre optic cables

Answer 1

The speed at which signals travel through telephone wires is determined by knowing the VOP (velocity of propagation) through a specified telephone cable.

VOP Defined:

"The speed of light in a vacuum is 186,400 miles per second. This speed is represented by the number 1 (100%). All other signals are slower. A cable with a VOP of .85 would transmit a signal at 85% of the speed of light. A twisted pair cable, which typically has a lower VOP (such as .65), can transmit a signal at 65% of the speed of light."

TELEPHONE Line VOP:

19 AWG Gel-Filled----68

22 AWG Gel-Filled----66

24 AWG Gel-Filled----62

26 AWG Gel-Filled----60



19 AWG AIR----72

22 AWG AIR----67

24 AWG AIR----66

26 AWG AIR----64



Polyethylene----66

Polypropylene----66

Teflon----69

PIC----67

Pulp----72

So, if you know the telephone cable type and VOP, you can calculate the speed of signal propagation over the line.

Answer 2

Propagation speed through a cable is dependent on the construction of the cable and the frequency of the signal. At RF frequencies two different coaxial cables can have Velocity Ratios of 66% and 85%, that's relative to the speed of light in a vacuum, 3x10e8 metres/second, so you could be looking at something like 120,000mph. Of course, thats purely in a cable, most signals get digitized somewhere in the chain and the delay in the coding and decoding will usually be a major portion of the overall delay unless theres satellite links involved.