66 On the Municipal Electric Telegraph, 
ors are seen diverging between the Stations, at which they unite 
in a single wire. | 
The general grounds for the division of the Circuits, according 
to their functions of Signal and Alarm, have already been stated. 
The immediate and practical reasons for such an arrangement 
will now be perceived. It is necessary, in the first place, to have 
so important a system under the control of some department of 
agent of the City government, and to provide for intelligent di- 
rection at its Centre. It is necessary also to provide means to 
complete the Circuit of the alarm bells with perfect regularity 
and at proper intervals, which would be impossible, except by 
machinery placed at the Central Office. It is also important to 
preserve the Signal Circuit distinct, that it may be available for 
purposes of police. 
In towns or Cities of small size, a single Signal Circuit and a 
single Alarm Circuit may be sufficient to include all the Stations 
which it is desirable to establish. In larger cities however, ad- 
vantage will be found in increasing the number of Circuits of | 
oth classes. In Boston, economy, both as regards length of 
conductors and battery power, induced the division of the City 
into North, South and South Boston Circuits. These arrange 
carried under the draw of the bridge, enclosed in a pipe. 
The Central Office, the Signal Stations and the Alarm bell Sta 
tions have all instruments peculiar to themselves. As the point 
from which the initial impulse proceeds in the actual operation 
of the System, the instraments and connections of the Si 
Stations will be first described. 
