1918.] The N.Z. Journal of Science and Technology. 
331 
AUTOMATIC TELEPHONE SYSTEMS. 
By J. N. Wallace. 
While working on multiplex telegraphy experiments in 1875 Alexander 
Graham Bell invented the telephone, and gave the first public exhibition 
of it at the Centennial Exposition in Philadelphia in 1876. At this time 
there were two classes of telegraph service in use—one consisting of a line 
with two or more telegraph instruments on it, the other consisting of several 
lines coming into a switchboard arranged for connecting any two lines 
together, so that service from one telegraph-line could be given over any 
other line coming into this exchange. It was quite natural that the 
telephone should be connected in the same manner from the time of 
its advent, and in 1877 numerous small telephone exchanges built on 
the principle of telegraph exchanges were installed in the United States. 
Different methods of signalling the operator at the central office, and in 
turn enabling the operator to signal the wanted telephone subscriber, were 
adopted ; but the general arrangement finally settled upon consisted in a 
small magneto generator at the subscriber’s station, with which he used to 
operate what is commonly known as a “ drop ” at the central office. 
Circuits on this principle were grouped into a magneto switchboard—the 
name “ magneto ” being obtained from the small magneto generator at 
the telephone subscriber’s premises. 
As the number of subscribers coming into any given central office 
increased it soon became impossible for one operator to do all the connect¬ 
ing necessary, and when a number of operators were employed it was not 
possible for any one of the number to connect directly from one subscriber 
to all the other subscribers in the exchange ; therefore a system of trunking 
was arranged, consisting of lines going from one operator’s switchboard or 
position to the positions of other operators. With this arrangement any 
subscriber calling in to the office would attract the attention of one 
operator, and she, on ascertaining that connection was desired with a 
subscriber whose line terminated in front of some other operator in the 
exchange, would connect the calling party’s line with one of these trunk 
lines to the other operator, and request the other operator to complete 
the desired connection. 
A later development in the art which was found to save considerable 
time in completing connections was to have a multiple of all the subscribed 
lines in the exchange appear in front of each operator in the exchange. In 
other words, supposing there were six operators in the exchange, certain 
of the lines would terminate in front of each one of the six, and each 
operator would answer calls on her particular lines. In addition to this 
termination there would be extra points on each line appearing in front of 
each one of the other five operators, so that any operator could complete 
a connection directly from a subscriber calling her to any subscriber who 
had access to the exchange, thereby doing away with the necessity of 
handling the call through two operators. As the business grew still further 
it became necessary to have more than one exchange in a given district. 
In order to handle calls under these conditions trunks such as were formerly 
used from one operator’s position to another were now extended from one 
switchboard to another switchboard in the same district, and a connection 
