Field Trial Touch Tone Trimline found

[paul-f]

While sorting through some 10-button Trimline sets, I noted the number "29" stamped on the metal plate under the number card of one handset.

Hoping it might be a field trial serial number, I opened the set and found the inside of the housing was marked F-56439  3-65!   

That is consistent with the pre-announcement trial in Chicago.

It's added to my site's Trimline timeline at: http://www.paul-f.com/weprotot.html#F56439

[WEBellSystemChristian]

Only you, Paul, manage to find random field trial sets in your own collection that you didn't know about before!!!

Did it come with the matching base? Do you know of any other FT [Touch-Tone (1220 style)] Trimlines that still exist? I've certainly never seen or heard of one!

[paul-f]

The set came with a standard production date-matching black desk base.

This is an example of being too lazy to open the handset housings to check the model number on each set in my collection that is "obviously" a 1220.

Lesson learned!

Most other field trial sets seem to be marked obviously on the outside or have external features which yell that they're field trial sets.

Now I'll always wonder whether there were other strange variations in the many Trimlines I've sold over the years.

Needless to say, I'll be looking inside Trimlines for quite a while.  I hope others find something interesting as well.

There are many other field trial Trimlines, as shown on the timelines on my site. 
   http://www.paul-f.com/weproto.html#TrimlineProto
   http://www.paul-f.com/weprotot.html#Trimline

I know of several other collections, including the hopefully saved models in the JKL Museum.
   http://jklmuseum.com/happy-birthday-trimline/

Several of the sets have been written up in Singing Wires over the years (including a 50th anniversary article I recently wrote for the August 2015 issue) and there are several reference charts in the TCI Library.

[poplar1]

Notice the inserts for machine screws on the deck; this carried over to production sets but only for a short time. Also, the recall button does not have the usual Bell System logo.

Link to TCI library for  BLR Jan. '66 article on Trimline development:
http://telephonecollectors.info/index.php/document-repository/doc_details/268-66jan-blr-trimline-development

[WEBellSystemChristian]

I should have elaborated on what I meant by 'more Field Trial Trimlines'. I know about the 'Schmoo' and 'Contour', but what about Touch-Tone development? Anyone know about any other TT Trimlines like Paul's?

[poplar1]

Did you see the chart in the article?  Trimline I (1960) and Trimline II (1963) were after DIH/Shmoo (1958) and Contour (1960), and before Trimline Production Set (1965).

[Jim Stettler]

I should have elaborated on what I meant by 'more Field Trial Trimlines'. I know about the 'Schmoo' and 'Contour', but what about Touch-Tone development? Anyone know about any other TT Trimlines like Paul's?

Regarding "Fat" modular (round button) sets:
The first TT trimline models had tone "coils" like a standard TT keypad. In 1968-69 WE was developing an IC based tone generator for the trimline. They produced some 10 button and possibly 12 button sets at this time. Around 1975-76 they started rebuilding a lot of the sets with the IC chip. I have noticed several variations of circuit design for these sets. I would assume the production sets at this time were also IC based.

As time went on they continued to make changes to these sets. The fat mod set was not discontinued when the square button sets were introduced. WE continued making the round button sets thru the break-up.

Since these sets were rebuilt in the factory there is not very much bsp info regarding the circuit changes so most collectors have no idea of the amount of changes that went into the board design.

Just an observation.
Jim S.

The attachment is about the new tone generating IC technology and compares the parts used.

The earliest IC chips were clear, Then I think gray and the late ones were black. The used different configurations of plastic "covers" inside the phone to protect the board.
You can find most trimline handset dates by removing the screw cover plastic.

Be carful replacing the plastic because it is easy to snap. I put them in a glass of hot tap water for a couple of minutes, dry it off and pop it in. If you do break the plastic you can use a number card plastic in it's place.