Y-3091 "Proposed Machine Switching Lineman's Handset"

[paul-f]

Discovery of the 1926 Y-3091 "Proposed Machine Switching Lineman's Handset" has added earlier info on the development of dial-in-handset sets within the Bell System -- leading to the Trimline announcement in 1964.

Read about it and see detailed photos and comparisons with other test sets in the article "Another Branch on the Trimline Family Tree," Singing Wires, May 2019.

The updated Trimline development timeline on my site is here:     http://www.paul-f.com/weproto.html#TrimlineProto