Development aspects of international voice frequency signalling and dialling under consideration by the C.C.I.F

After the introductory section the question is considered under the following heads: importance and necessity of voice frequency signalling, comparison with d.c. and other a.c. signalling systems, interference between voice frequency systems, recommendations to avoid this interference, time variations associated with voice frequency signals, choice of frequency for the prefix signal, voice immunity tests, determination of length of prefix, efficiency of the guard circuit, considerations controlling the general arrangement of the voice, frequency code of signals, signal code timing, transit working, summary of research work in progress and questions awaiting consideration. The paper concludes with a glossary of terms, a translation of the proceedings of the 3rd Commission of Rapporteurs at Oslo and a Bibliography.