Need Signal Lamp Base(s,) "Re-Based" Style

NW Mailing List nw-mailing-list at
Tue May 8 18:18:33 EDT 2012

I am in need of one or two "re-based lamp sockets."  These were used in signals and I need at least one (preferably two) to put together a little display of the various types of signal lamps used over the years.

The principle of "re-basing" signal precision lamps came around about 1915, when the "doublet lens" signal  was invented and the Position Light Signal was under development .  The optics of those two signals required that the concentrated filament of a signal precision lamp be located within 1/64th inch of the optically precise focal point behind the lens.  Lamp m anufacturers of the day could not made lamps to such a close tolerance so, according to the articles written by Alexander Holley Rudd, the railroad(s) set up a shop to do the work.  Lamps set up in a jig were positioned by hand  so that the filaments were in the critical location, and a copper collar was then soldered around the base.  In order to maintain the precise position of the filament  when the lamp was installed in a signal, "bayonet" side pins were stamped into the "re-base" collars, and these mated with matching openings in the socket so that, once installed,  everything was held in in  proper registration and position.

Later (according to the literature,) the lamp manufacturers themselves began making lamps with re-bases and precise orientation of the filaments, and railroads no longer had to do the r e-basing in their own shops .  Union Switch & Signal products used re-based lamps having two bayonet side pins, but General Railway Signal Co. built its signals to use re-base lamps having three bayonet side pins... so that the customers could not buy from the "other manufacturer" should the price be cheaper !

At some date which I have not yet determined (but probably in the late 1930s,) the lamp manufacturers decided to cash in on the "signal precision" filament orientation market  and began marketing signal prec ision bayonet lamps in the same configuration you use for your 12-volt automotive tail lights.  At that point, railroad signal manufacturers switched to the new configuration and adapter bushings were provided for using the new type lamps in  the old re-based sockets remaining in service (many of which surveved into the 1980s, possibly later .)

There were hundreds of signals around in the 1980s still equipped with sockets for re-based lamps, but they were all in G RS signals and at that time I was not restoring GRS products and never brought any of the re-based  lamp sockets home.   The early N&W PL signals were no doubt  equipped with re-based lamps, as that was the technology of the time period.

The attached photograph shows close up views of a re-based signal precision  lamp and its socket.  The sockets measure about 7/8" inside diameter.  This photograph shows a lamp and base with three side-pins, but I will take what I can get. 

Not looking for any freebies...  If anyone has a couple to spare, I'll buy and pay shipping.  And I shall not be picky about the material on which the re-bases are mounted (porcelain, phenolic or broken) as I can make my own.

-- abram burnett

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