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Slide projectors soon used the 24 V 150 W lamps that had the
G17q base. This base was a modernisation of an old construction.
Pathé used a strip beside the base to place the small 6 V 0.5 A lamp
in its exact position. Bell and Howell did the same, using a strip on
the special B&H plate.

The G17q had a round piece of steel
with a ripple in the middle and had four
pins on the bottom. This base was
called ‘Tru Focus’. The pedestal of the
projector was used as a claw so that the
lamp was firmly located and held. This
base was mostly used in the slide pro-
jectors. In the beginning the 24 V 150 Fig 9. Left: Bell & Howell,
Fig 10. G17q Base W lamps used in slide projectors had the and right: Pathé
same base.

The lamp manufacturer Radium produced a 12 V 150 W lamp
with the G17q base that was used in the best Bauer movie
projector of those days: the T10R. But other factories did not
follow and Radium stopped production. As a result thousands of
Bauer T10R projectors could no longer be used. Later Flecta put
this type into production but from that time the Bauer T10R
projector became infamous. The 12 V 150 with a Ba15s base was
produced by a French factory but no projector brand followed.

Philips, in combination with Eumig, produced
a 12 V 100 W lamp with the Ba21s base. It was
a thick base with some pins outside to better
centre the lamp. This was used in the Eumig Fig 11. Bauer T10R lamp.1
P8M projectors, but no other factory used it.
There then appeared a 115 V 150 W lamp with
the G17q base that had a little plate in front of
the filament so that the light had to get to the
lens via the mirror. This was an American
development that allowed you to manipulate
Fig 12. 12 V 100 the light via the mirror. For example, the Ko-
W with Ba21s dak 10 E lamp had a mirror outside close to the
base.
lamp. Fig 13. Kodak 10E lamp.
So it was to be expected that the Americans should
put the mirror inside the lamp. And they did. The
glass of the lamp was like a bell glass over the light
unit. In Photo 14 you can see the lamp on the left
with this plate. The middle lamp was placed hori-
zontally and was used in the Kodak M 2 super eight
movie projectors.
Fig 14. Left: 115 V 150 W with plate. Middle: lighting for the Kodak M2. Right: normal lamp.