Incandescent vs. LED dial lights

[poplar1]

If you look on the dial number plate on a Western Electric rotary Trimline, where the letters and numbers are printed, between the 1 and the 0, there may be the letters "LED", if it's indeed got a line-powered LED to illuminate the dial.

These LED dials for Trimlines were introduced around 1974 (not sure of exact date), or about the same time that the phones were going modular so that they could be picked up at the phone co. stores. The houses and apartments were being converted to modular so that the customers could hook up the company-owned phones themselves, in order to save the cost of dispatching a technician.

So for a while, the rebuilt Trimlines with incandescent dial lamps -- which required a separate transformer -- were retained for the installers/repairmen to carry on their trucks; but in the Bell stores, the "LED" Trimlines were more prominent. Eventually, all new Trimlines had LED dials, and Bell-company phones returned to Western Electric for rebuilding were upgraded with LED dials. The Touch-Tone LED Trimlines are more easily spotted because of the square buttons on the dial, rather than round.

The Princess phone, on the other hand, continued to have an incandescent dial lamp/night light for another 20 years, until about 1993, when the Signature Princess -- coded 2703BMG -- was introduced with an LED-illuminated dial, which was powered by the telephone line. However, for the night light feature, a transformer "kit of parts" was still required for the Signature Princess.

While earlier BSP issues stated that one 2012A transformer was required per dial light (Trimline) or dial/night light (Princess), later versions stated that any number of Trimlines could be connected to one 2012A transformer, so long as the customer did not plan to have more than one phone off-hook simultaneously. For Princess phones, each set required its own 2012A or 2012C transformer, because the night light could be turned on even when the phone was hung up, thus reducing power available to other Princess or Trimline sets if they were sharing the same transformer.

There were larger transformers available where multiple phones shared the same premises. There were still limitations on how many sets could share the same feeder pairs, even with these larger transformers. And, as always, it was not recommended to use 25 foot mounting cords, because the increased resistance of the cord would cause the lamps to be less bright.

[19and41]

My beige rotary trimline has the LED illumination,  It appears more to be for edge lighting of the dial letters and numerals, as opposed to illuminating the number card window.

[poplar1]

My beige rotary trimline has the LED illumination,  It appears more to be for edge lighting of the dial letters and numerals, as opposed to illuminating the number card window.

I don't think they ever intended to light up the number card window. In fact, in the first issue of the BSP 502-303-101 for Trimlines, the transparent number card window goes on the AD1 base, and the handset has a matching color plastic piece (opaque):

See figure 1 (220A hand telephone set) and Figure 3 (AD1 base) in this BSP from TCI library.

http://telephonecollectors.info/index.php/document-repository/doc_details/2762-502-303-101-i1-reference-220a-hand-tel-set-w-ac1-ad1-bases-tl

Someone may want to post the photos here; I can't remember how to extract photos from the TCI files.

[Phonesrfun]

Someone may want to post the photos here; I can't remember how to extract photos from the TCI files.   

How's this?  Windows snipping tool.  Invaluable for this sort of thing.