The lights on the engines and those at gauge glasses and water
columns and at the pumps are supplied by direct current from the
250-volt circuits. All other incandescent lamps and the Nernst lamps
are supplied through transformers from the 60-cycle lighting system.
[Sidenote: _Emergency
Signal System
and Provision
for Cutting Off
Power from
Contact Rail_]
In the booth of each ticket seller and at every manhole along the west
side of the subway and its branches is placed a glass-covered box of
the kind generally used in large American cities for fire alarm
purposes. In case of accident in the subway which may render it
desirable to cut off power from the contact rails, this result can be
accomplished by breaking the glass front of the emergency box and
pulling the hook provided. Special emergency circuits are so arranged
that pulling the hook will instantly open all the circuit-breakers at
adjacent sub-stations through which the contact rails in the section
affected receive their supply of power. It will also instantly report
the location of the trouble, annunciator gongs being located in the
sub-stations from which power is supplied to the section, in the train
dispatchers' offices and in the office of the General Superintendent,
instantly intimating the number of the box which has been pulled.
Automatic recording devices in train dispatchers' offices and in the
office of the General Superintendent also note the number of the box
pulled.
The photograph on page 120 shows a typical fire alarm box.
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