Staged Fault Testing of Leased Audio-Tone Relaying Channels Subject to Ground Potential Rise and Induced Voltage

A series of staged power-fault tests was conducted by the U. S. Bureau of Reclamation with the Bell System participating. One of the main purposes of these tests was to observe the effects of power-system disturbances on leased audio-tone relaying channels. Interference on these circuits was minimized by using bifilar-wound loading coils to avoid signal modulation effects; high-potential testing of telephone cable facilities ensured adequate dielectric strength. In addition, a communication-facility electrical protection system was installed which employed longitudinal drainage that was applied as needed to mitigate 60-Hz potentials introduced into the telephone plant.