TELEGRAPH INNOVATION.

Manawatu Standard, Volume LIX, Issue 69, 18 February 1939, Page 8

TELEGRAPH INNOVATION.

VOICE FREQUENCY SYSTEM. New Zealand’s latest telegraph development—the use of the multichannel voice frequency system—came into practical use between At ellingtou and Christchurch three months ago and proved its value during the Christmas rush of telegraphic business. On one pair of wires the Post Office engineers are able to provide three channels in each direction for telegraphing by the multi-channel voice frequency system, while each of these channels is also available for working four channels of the multiplex telegraph. But the use or the single pair of wires does not cense with the telegraphic channels, because this metallic circuit is ■ also able to accommodate without overcrowding or interruption of other messages three clear telephone s(>eecli circuits, making a total of twenty-seven complete channels of communication simultaneously on one pair of wires. The new system, which is the latest development in telegraphic communication, showed another improved advantage during a long dr.v spell in January, when telegraphic circuits close to the coast on the North Island and betwene Blenheim and Ivaikoti.ra gave trouble owing to the partial breakdown of the insulating properties of the insulators on the telegraph p.oles due to encrustations of salt contained in sprav driven ashore by nor’-west gales. Ordinary telegraph operation which utilises an earth return was made difficult, but tlie multi-channel voice frequency service continued without difficulty, as the existence ol a complete metallic circuit enabled reduced insulation to l>e overcome I>v it slight increase in power on tlie amplifiers. The same advantage was shared on the long distance telephone carrier circuits. Salt encrustation of insulators on high voltage, power transmission lines in the Wellington district during the same periotl caused serious interruption in the power supply. An installation of multi-channel voice frequency telegraphy is being provided between AVellington and Blenheim and also lvetween Auckland and AVellington. The latter equipment will probably be .completed by the end of February, giving six telegraph channels in each directioimwlulo still allowing for three telephone channels between the two centres over the same pair of wires. Over the six telegraph channels it will he possible to provide another four channels of the multiplex telegraph.