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542A Subset

Started by tallguy58, February 03, 2014, 11:29:17 AM

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tallguy58

Cheers........Bill

poplar1

It's a sidetone subset with line and hold relays for 2 lines, also has battery feed for intercom, and ringers for each line with different sounding gongs. Could be used with 440 Key Sets or with separately mounted 6021 Keys used with single line phones. They were installed as part of a "wiring plan." There was also a single line version (541A). The anti-sidetone versions were 641A and 642A.
"C'est pas une restauration, c'est une rénovation."--François Martin.

poplar1

The addendum to C66.507 cited shows in Fig. 7 the replacements for these prepackaged subsets: that is, the 1A and 2A Key Telephone Units (KTUs) for holding and intercom. 1938 was also the year that the 440 and 460 (multi-line 302s) were introduced.
"C'est pas une restauration, c'est une rénovation."--François Martin.

tallguy58

Amazing.
Where do people find this stuff?

I guess this whole gizmo was eventually replaced by a Call Director.
Cheers........Bill

poplar1

#4
The 541A/542A/641A/642A Subsets were originally used with single line sets and externally mounted keys. Circa 1938, 1A and 2A KTUs (Key Telephone Units)--or 1A Key Equipments- replaced the 542A etc. subset. 1A Key was replaced by 1A1 Key in the 1950s, and 1A1 was replaced by 1A2 c. 1964.

The new 1938 keysets (440/460) included the induction coil, condenser, and one ringer, along with the keys. They could be used with either the new 1A and 2A KTUs, or with the 1- and 2-line (542A etc.) subsets by bypassing the subset's induction coil and talking condenser. Separately mounted keys were still needed with hanger phones (211 for example), also for wall phones, until the 851 wall set was produced.

I would probably say the Call Director set, along with the 540- and 560- series 4- and 6-button keysets, replaced the earlier single line desk sets used with externally mounted keys, and also the 400 series keysets.

And the closest descendant of the 542A Subset might be the 551A/B/C KSU ("shoebox,") a self-contained 1A2 KSU (Key Service Unit) for up to 4 lines or for 3 lines and manual intercom.
"C'est pas une restauration, c'est une rénovation."--François Martin.

Sargeguy

These show up on eBay about once per year.  I believe the last one sold for about $225 or so.
Greg Sargeant
Providence, RI
TCI /ATCA #4409

poplar1

Some were sawn in two in order to make two subsets during World War II.
"C'est pas une restauration, c'est une rénovation."--François Martin.

tallguy58

Fantastic info.

Thanks guys.
Cheers........Bill