Trimline telephone

To miniaturize the rotary dial sufficiently to fit in the Trimline handset, the designers invented an unusual moving fingerstop.

[2] Based on the trials, Western Electric modified the design several times, ultimately resulting in the Trimline, which was eventually introduced in 1965.

The Trimline included a lighted dial and was encased in a sleek, curved molded-plastic housing that took up less space than earlier Western Electric telephones.

The bulky transformer and the need for a conveniently-placed outlet was criticized by many consumers, but was necessary because of the power demands of the incandescent light bulb.

Years later, Western Electric redesigned the Trimline to use a low-power green light-emitting diode (LED) to backlight the dial, which was powered by current from the telephone line, eliminating the need for the transformer.

Always eager to re-use its older stocks of turned-in rental phones, AT&T later repainted and sold early-model non-LED Trimlines as "non-lighted" models, without a transformer.

In the Trimline version designed for connection to an RJ11 telephone jack, pins 2 and 5 (black and yellow) may carry low-voltage AC or DC power.