AUTOMATIC EXCHANGE.

Auckland Star, Volume LXIII, Issue 78, 2 April 1932, Page 7

AUTOMATIC EXCHANGE.

NEW TELEPHONE SYSTEM. WHANGAHEI IMPROVEMENT. OPENING TO-MORROW. (By Telegraph.—Own Correspondent.) WHANGAREI, this day. For over a year the work of installing an automatic telephone system has been going ahead quietly, and the change-over from the old to the new will take place at 7 o'clock to-morrow morning. In January, 1931, apparatus arrived from Stockholm. Three local experts and eleven others from all parts of the Dominion have been under the supervision of Mr. G. 1!. Milne, installing engineer for the New Zealand Post and Telegraph Department, and Mr. M. Linderoth, of the Ericsson Company, from Sweden. Down in the basement are two batteries, which do away with the separate batteries in each of the old telephones. Only one of these 24-volt batteries is in use at a time, the other being re-charged by an electric generator. Remarkable Ringing Machine. Perhaps the most wonderful feature of the ringing machine in the main exchange room is that not only does it give ordinary rings for private line owners, but also rings a special code for rural lines. The code consists of a system • of short and long rings, and in place of the old system, of using letters for the different members of a party line, the code is rung by a combination of the numbers.

So delicate is the apparatus, which actually puts the connection through, that elaborate precautions have to be taken against the invasion of dust, and to militate against the humid atmosphere with which Whangarei is endowed, and in a side room is situated a plant which filters and warms the air which passes into the exchange room. All the windows will be kept closed, and the only air which can come into the room _ must come through the heating machine. The air is drawn through shutters and taken throusrh a muslin screen. It is then propelled by an electric fan through a steam-heating arrangement before going into the room. Precautions Against Leakage. The heated air absorbs any moisture which would cause a leakage and is drawn out through ventilators in the roof.

The system installed in Whangarei is commonly known as the unit system.

The subscribers' lines are grouped into lots of 500, and the arrangement of the apparatus is thus, that each row of machinery contains all the mechanism necessary to make a complete call. Every line is put through to the switches, of which there are three, all almost similar in construction, but each performing a different duty. The "brains" of the whole automatic system is tho register, which acts as a mechanical operator. It record. the number dialled and connects up with the line calls.

To every group of 500 lines there are ten registers. They are in use only during the period of dialling and then are disconnected. Before putting the connections through, the switch tests the line to see if it is in use or not. The line is connected up and the ringing current sent out to sound the bell of the wanted telephone. The system of alarm is elaborate, and if for any reason the switch does not return to its position after being disconnected, a light is shown and a bell automatically rings, thus locating the defective switch. The old exchange is to be dismantled, overhauled in Auckland, and later installed in a suitable centre.