Cab, Its a 3 wire (Ground lead) for testing cable pairs. It can be used to test Tip/Ring grounds and to 'Kick" the cable for distance. Very basic compared to what the tech's use today. 43 years in I&M but mostly Key telephone and Switching systems in US ARMY.
One wire DC circuits are kind of simple if you 'Divide and Conquer'. Split it down to sections and go 1 step at a time. Any connector is subject to failure, any ground can go open and any relay or switch can fail.
Retired, US ARMY 1973-1994
ASE mechanic, Electrical 1994-1997
Retired GTE/VERIZON/FRONTIER 1997-2015
Posting cheap tech help (CRAP) here since Nov 97, 1000's of posts, some may be good.
03 Suzuki Burgman 650(Burger King) Scooter
65 Formula S Cuda
78 Little Red Express Truck
98 Buick Regal (wifes car)
| 
