5 ms·

WW2 stories of diversions to enemy communications: put small needles through the cable. At first you'd think you just have to cut the cable, but that actually m

WW2 stories of diversions to enemy communications: put small needles through the cable. At first you'd think you just have to cut the cable, but that actually makes it very easy to find and fix the problem. Small needles that short the wires are very difficult to locate. Unless you have a fast device that measures return latency on the shorted circuit, but that wasn't available in the 1940s.

bradknowles 4y ago
It's called a Time Domain Reflectometer. They're pretty cheap. For RG-58 style coax, you can get hand-held VeEX CX41 units for a few hundred dollars. I'm sure that TDRs for other types of cables shouldn't be too much more expensive.
jutrewag 4y ago
Perfect time to use a pin nailer.
- tonyarkles 4y ago
  Customers used to do this unintentionally with staples, and my boss was too cheap to buy a TDR tester for a long time
tialaramex 4y ago
However "a fast device that measures return latency on the shorted circuit" is presumably very cheap today. 20+ years ago, rewiring buildings for 1000baseT the Cisco switches (3650s maybe? 3750s? I know they had IPv6 multicast acceleration in the switch fabric because that's why we had them) would do this for any circuit on command, OK, 18 metres from here there's a fault, pace, pace, pace, I reckon it'll be up on this cable tray... yup, some fool tried to "repair" a broken Cat5 cable, we'll just rip it out, meanwhile patch to a different circuit.
- sandos 4y ago
  I believe I even had a BIOS in a PC that did this in some way.... Actually, I think it wasn't detecting faults but rather the length of cable connected.
- jmole 4y ago
  Time Domain Reflectometry - https://community.cisco.com/t5/networking-knowledge-base/how-to-use-time-domain-reflectometer-tdr/ta-p/3119327 https://community.cisco.com/t5/networking-knowledge-base/how...
cjbgkagh 4y ago
You can use binary search to find the pin. Unless two or more pins are used.
- monocasa 4y ago
  At that point it's easier just to run new line.
  - cjbgkagh 4y ago
    But you don’t know that when you start. You could assume it and never try to repaid and always replace but in WWII there were not as many options.

bradknowles 4y ago

It's called a Time Domain Reflectometer. They're pretty cheap. For RG-58 style coax, you can get hand-held VeEX CX41 units for a few hundred dollars. I'm sure that TDRs for other types of cables shouldn't be too much more expensive.

jutrewag 4y ago

Perfect time to use a pin nailer.

tonyarkles 4y ago
Customers used to do this unintentionally with staples, and my boss was too cheap to buy a TDR tester for a long time

tialaramex 4y ago

However "a fast device that measures return latency on the shorted circuit" is presumably very cheap today. 20+ years ago, rewiring buildings for 1000baseT the Cisco switches (3650s maybe? 3750s? I know they had IPv6 multicast acceleration in the switch fabric because that's why we had them) would do this for any circuit on command, OK, 18 metres from here there's a fault, pace, pace, pace, I reckon it'll be up on this cable tray... yup, some fool tried to "repair" a broken Cat5 cable, we'll just rip it out, meanwhile patch to a different circuit.

sandos 4y ago
I believe I even had a BIOS in a PC that did this in some way.... Actually, I think it wasn't detecting faults but rather the length of cable connected.
jmole 4y ago
Time Domain Reflectometry - https://community.cisco.com/t5/networking-knowledge-base/how-to-use-time-domain-reflectometer-tdr/ta-p/3119327 https://community.cisco.com/t5/networking-knowledge-base/how...

cjbgkagh 4y ago

You can use binary search to find the pin. Unless two or more pins are used.

monocasa 4y ago
At that point it's easier just to run new line.
- cjbgkagh 4y ago
  But you don’t know that when you start. You could assume it and never try to repaid and always replace but in WWII there were not as many options.