332 The N.Z. Journal of Science and Technology. [Nov. 
would be handled through two operators—one in the office in which the call 
originated, and one in the office of the line to which connection was desired. 
Systems operating as above were used for a number of years, and then 
it occurred to telephone-designers that some simpler and cheaper method 
of attracting the attention of the operator might be obtained, and a number 
of exchanges were installed in which the simple removing of the telephone 
from the switch-hook operated a calling-device at the central office by 
means of current flowing through this device from the central office out 
over the subscriber’s line. These calling-devices at first were magnetic 
signals, and later small incandescent lamps were used. During this period 
the subscribers continued to use small primary batteries at their stations 
to supply current for talking purposes. 
All this while develop¬ 
ment was being rapidly 
carried out, and in 1896 
the first common - battery 
switchboard was installed. 
This marked a great ad¬ 
vance over all previous types 
of switchboards. In this 
system the battery-current 
for both signalling and talk¬ 
ing purposes was furnished 
from the central office, doing 
away not only with the 
magneto generator at the 
subscriber’s station, but also 
with the primary batteries, 
which had always been a 
source of considerable an¬ 
noyance and expense to the 
telephone companies. 
Since 1896 common- 
battery systems have been 
generally adopted in all 
large exchanges throughout 
the world, and although 
many refinements have been 
made to the system, and the 
talking efficiency and sim- Fig. 1 . —Subscriber's dial, 
plicity of operation in the 
exchange greatly increased, no radical changes in underlying principles were 
made until the advent of the automatic telephone systems. 
Experimental and development work on automatic systems was com¬ 
menced as far back as the time when common-battery systems were first 
being seriously considered, and some designs of these systems, more or less 
satisfactory in operation, have been on the market for about twenty 
years ; but it is only within the last decade that they have attained such 
perfection that the British Government has considered it advisable to install 
such systems in its exchanges. 
The difference between automatic systems and previous systems, which 
are now all classed under the general heading of “ manual ” systems, is 
