Introduction
Bristol East Illuminated
A few photos
Photographers
Maurice W Earley
Collection with NRM? - APRoGWS page 72
Adrian Vaughan
APRoGWS page 41
Track Circuit Lamps
T2 - 7mm Telephone Slide Base Filament Lamps
Filament lamps will perform to specification and give optimum life
when:
a) they are powered at the rated voltage from a stabilised 50 Hz
A.C. supply
b) ambient temperature is in the range 20°C to 25°C
c) no mechanical vibration is present.
Deviations from these criteria can have a significant effect on
lamp life, particularly with low current filaments (<80 mA).
Operation from a d.c. supply at rated voltage can reduce specified
life by up to 50%.
The effect of variation from the rated operating voltage should
be noted:
5% above will reduce lamp life by up to 50%.
5% below will significantly increase lamp life.
Current consumption can vary by up to ±10% on stated values
at rated supply voltage. Care therefore should be exercised when
running a number of lamps in series. In such applications it is
recommended that the rated voltage be reduced by 10% to prevent
premature failure of individual lamps.
Technical specification
Voltage 12V
Current 100mA = 0.1A
Lumens 3
MSCP 0·24
Average life (hrs) 2,000
1 ampere = 1 000 milliamperes
123 Track Circuits = 246 Lamps
246 x 0.1A = 24.6 Amps
P=IV 24.6 x 12 = 295.2Watts
Further Reading
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Bristol Signalling 
