THE MICROPHONE AT WORK.

Auckland Star, Volume XXXIV, Issue 149, 24 June 1903, Page 6

THE MICROPHONE AT WORK.

A member of the Dunediu Engineers who attended the Barewood camp says: "We had our new microphone at work over a mile and a half of insulated wire, a bayonet driven into the ground at each station taking the place of earth plates. The Instrument worked splendidly, and ' communication was kept up day and night continuously between headquarters and the central piquet. For the practical working of the circuit only two cells at each onvl were required, and as an experiment the battery was once temporarily cut out of circuit. The instrument, however, continued to audibly reproduce sounds spoken into the sensitive microphone at the distant station. This effect is explained by the difference in potential at the two stations

nfljnsttng itself by means of the line wire. Those earth currents traverse the circuit just as an ordinary current does, but they are very feeble, and this suffices to demonstrate the very great value of the microphone in the field, and on active service. Instead of the usual bell, which might attract the attention of an alert enemy, a make-and-break induction coil

and a telegraph key are inserted into the circuit, and on depressing the key a muffled. buzzing sound, audible only itot those near the Instrument, is heard. It can be worked over long circuits with a small battery, «nd should there exist any possibility of the circuit being tapped by the enemy, it may be used as a telegraph instrument pure and simple, no increase of battery toning necessary- For moving columns, where portability is of almost paramount importance, this instrument seems to have n great advantage over the ordinary field telegraph set, which is more cumbersome, less easily adjusted, and requires a much •larger amount of battery power. It would lie interesting to experiment with a view to finding out what the microphone could <be relied on to do over a long circuit, and perhaps permission could be obtained to use the Government telegraph lines on eoine camp Sunday, when thy would probably not be otherwise engaged."