PICTURES BY WIRE.

New Zealand Herald, Volume LXV, Issue 20105, 16 November 1928, Page 17

PICTURES BY WIRE.

SYDNEY TO MELBOURNE.

EARLY SERVICE PROMISED. [FKO.M OUU OWN COURLSI'ONDK.N'T. ] SYDNEY, Nov. 8. In six months' time, according to a promise made by tlie Commonwealth Director of Postal Services, there will be inaugurated the regular transmission of photographs and other pictures by wire between Sydney and Melbourne. It is anticipated that this service will bo of great valuo to tho newspapers. But not only will tho press benefit, but the service will be of incalculable value to the police, who will be able to transmit not only the photographs of wanted men, but their finger prints as well. This should bo an important factor in the detection of crime. Then, again, it is expected that tho banks will use tho service fairly freely, for they will bo able to transmit, with no more difficulty than they now communicate by telegram, any signature. It will bo possible to transmit plans, drawings, in fact, almost, anything. Tho means by which a picture is, metaphorically, rolled up and squeezed through a thin wire to emerge at the other end, 600 miles away, in its original form, is interesting. An ordinary photograph is handed in at the Post Office in Sydney, for example, for transmission to Melbourne. It is taken to the telegraph operating room, placed on a cylinder on the transmitting apparatus, where a tiny beam point of high-power light falls upon it as it is rotated in the cylinder. Tho light is reflected from the picture on to a photo-electric cell —a cell sensitive to light variation —and the variation in the intensity of the refracting ray, which traverses the entire area of the picture in a series of minutes lines, produces a corresponding variation in the emission of olectrons from the cell. These electronic variations give rise to currents of varying strength in the transmitting circuit, according to the varying light and dark patches met by tho point of light as it ! traverses tho picture. These varying currents are then amplified and trans- ! mitted through the ordinary telegraph lines to tho receiving apparatus at the office of destination.

In the receiving apparatus a strong beam of light is passed through an "optical" system, consisting of what is known as a "Nicol" prism, a Kerr cell, and another "Nicol" prism. This combination is sensitive to the varying currentinduced by the transmitting current at the office where the picture was handed in. Tlio quantity of light passing through this system is varied according' to tho amount of current received. And so tho emerging light corresponds with the original picture, that is, in light and shado. Tho received beam of varied light is focussed upon a sensitised Film on a cylinder rotating in synchronism with the transmitting drum, of which it is (he counterpart. As the drum, rotates, the varying light falling upon it is photographed 011 tho film in a series of lines that are so thread-like that when the negative is developed, it is almost impossible to distinguish tho transmitted picture from the original. Tho transmitting of pictures by wireless. which is performed upon the same principle as tho sending of pictures' by wire, with modifications, is the next step. Already certain Australian enthusiasts nre experimenting with this branch of the science, and considerable progress has been made in the transmission of still pictures. Abroad the regular transmission of pictures by wireless is an established fact, and here in Australia it is promised that people will be able to look in next year as well as listen-in. The charges for the transmission of picturegrams next year has not been decided, but the promise has been made that they will be reasonable enough to permit of full use being made of the service.