Power Feeding and Personal Safety in Cable Transmission Systems

The repeaters in telecommunication cables are power fed. Currents of up to 0,5 amperes flow at potentials of up to several hundred volts. To ensure that no one is injured if he touches the projecting live conductor when working on an undamaged or damaged cable, even if the power feeding is switched on, such circuits are designed with the following considerations in mind: The power-feeding circuit is symmetrical and is balanced to ground with high impedance at the feeding point only. The switch-attachment needed in any case for fault location for every repeater ensure that the contact voltage remain harmless and low in the event of a fault. Power-feeding terminations are available for rendering the work site safe when lengthy work on the cable is necessary and transmission has to be simultaneously maintained.