Type AT Signal - Alstom

Introduction
1.3.1. Housing
The signal housing is of cast-aluminum construction. Access to the internal parts of the
signal is made through a hinged door at the rear of the housing.
The Type AT 3 Aspect Signal is internally divided into four potentially active light
compartments. Three compartments are used for aspect signals and one for the
number display (number plate, illuminated (incandescent) number or LED number). The
door of the three Aspect signal is equipped with two ventilators to prevent moisture and
heat build-up within the housing and a gasket with sealant to prevent water from
entering the housing.
The Type AT Single Aspect Signal is available with or without an enamel number plate.
The single aspect door has one ventilator. A latch is provided to padlock the door and
prevent unauthorized access.
Housings can be stacked to make 4, 5, 6, 7, or 8 aspect configurations.
VENTILATORS
4 COMPARTMENTS IN
A 3 ASPECT SIGNAL
NUMBER PLATE
Figure 1-2. Typical Three Aspect and Single Aspect Type AT Signal Housings,
Side View
P2502, Rev. Apr/08 1–4 Alstom Signaling Inc.