New open-wire carrier telephone systems in the frequency range up to 300 kilocycles/second

In common with the other telecommunication administrations of the world, the South African Post Office experienced an unprecedented increase in the demand for trunk telephone facilities after the last world war. This has not yet abated and, in truth, has been accelerated further by the introduction, first, of subscriber trunk dialling (STD), then of national subscriber trunk dialling (NSTD).