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Rotary Set Development Timelines

Chronological Summary and Highlights, presented by model produced.
Click photos for additional details, if available.

2005-20 paulf.  All rights reserved.
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ON THIS PAGE:     300    500    PRINCESS    TRIMLINE    Others 

This is a work in progress.  Please send additions and corrections.
I'm sure there are many "missing links" to be discovered.

For background, read the DEVELOPMENT OVERVIEW.

WE 302 development timeline -- announced in 1936
Design goal: Produce a combined set (telephone and subset in one compact unit).
Octagonal Base

Octagonal base

Octagonal base concept, wood design model

Y-3290  7/10/29

An interesting alternative to the rounded D1 mounting.


Concept set, wood design model

Y-3419-19  1/24/31

Combined set using some design cues from the D1 mounting and octagonal design above.

(Images courtesy of AT&T Archives and History Center, San Antonio.)

WE 302 prototype Long

D-95647  IV 32

Long metal case with ringer positioned in the rear.

 WE 302 prototype in Bakelite

D-97464  I 36 & II 36

Short case looks very similar to the production model.

Found with either bakelite or metal housings, with a metal base plate.

Later models had a F1-like handset.

WE 302
1936  -- WE 302 as announced

Original cradle accommodated both E1 and F1 handsets.

Case was cast metal, baseplate was metal.

For details on models produced, go here: WE 300-SERIES  
3xx keyset prototype
Prototype for a 15-line keyset.

(Courtesy of Lucent.)

500 desk set development timeline -- announced in 1949
Design goal: Produce a set that compensates volume level for distance from the central office.
G Handset
                  Patent Drawing

500 base
                  Patent Drawing

WE 500
                  Patent Drawing 1948
1946 - Henry Dreyfuss' firm began work on the 500 external design.  Effort led by Robert Hose.

Some 2500 sketches were made.  Handsets were primarily modeled in wood, while bases were initially in clay and the most promising cast in plaster and lacquered.
  (References: Designing for People, Henry Dreyfuss, Simon and Schuster, 1955; Designing the Telephone, Bell Telephone Magazine, Summer 1955; Henry Dreyfuss, Industrial Designer: The Man in the Brown Suit, Russell Flinchum, Rizzoli, 1977;  A Conversation with Donald Genaro, Singing Wires, Vol 18, No 10, Oct 2004.)

June 1947 - G handset Design Patent filed. 

March 1948 - Base Design Patent filed.

Sept 1948 - Line Switch Patent Application filed.  Housing shape updated.

April 1949 - Ringer Patent Application filed.

Line Switch
                      Patent Drawing  Ringer
                      Patent Drawing
(Click on image for larger view)

Hookswitch:  Arms changed from horizontal to vertical orientation for before production.  Mounting and dust cover design simplified.

Ringer: Casting redesigned to permit 2 mounting screws instead of 1 before production.
Pre-production set 1948  Pre-production.

(Best guess based on research to date.  Watch for updates.)

Internal components similar to the patent drawings.

Aluminum dial mount. Plastic fingerwheel.
Bell coil wrapped in olive cloth (like 302s B1A).

Aiming dots, visible through the fingerwheel holes, were added during the development process to help improve dialing speed and accuracy.

Field Trial of 50 pre-production sets.  (BSTJ*, 4/51)

(Photo from Pacific Tel Magazine, May/June 1949.)

*Bell System Technical Journal
Early production 500 set,
1949, November.

Internal components modified to satisfy manufacturing and service considerations.  Metal fingerwheel.

There were several configurations of the dial ring, with different legends at the "0" location.  One has 0, OPERATOR, and Z (as the set above).  Another has 0 with OPERATOR underneath in an arc.

Field Trial of 4000 early production sets in 10 locations, including Manhattan, Staten Island, Chicago, St. Paul, St., New Orleans, Los Angeles and San Francisco.  (BSTJ, 4/51)  Also St. Louis. (From an internal Bell System memo in the AT&T Archives)

Go to component comparison photos.
Early production 500 set, as announced. 1949 -- WE 500 as announced

June 2, 1950, "The first supply of new 500-type telephone sets was announced.  About 180,000 were expected to come off production lines during the balance of the year." (Events in Telecommunications History, AT&T)

For details on models produced after introduction, go here:
    WE 500-SERIES

(Photo of a dial dated 10/49 in a 1950 phone. This dial ring style was used until mid-1950.)
Use this link to the Touch Tone Desk Set Timeline
To Touch Tone Development Timeline

 Princess development timeline -- announced in 1959
Design Goal: Produce a compact set with lighted dial suitable for a bedroom extension.
Bedroom set model
ca. 1955 - 1956

Numerous design concept models were made from wood.

Additional sets...
WE Bedroom Phone

F51910  3/57 - "Bedroom Telephone"

Full size dial (#6 style), Light switch on front.
Electronic Ringer or F52510 external ringer.

Product trials in Columbus, OH and San Leandro, CA.
400 sets in each city.  Tested with Demitasse and Ericofon to determine customer preference for dial placement.

Market trials in Norristown, PA and Peoria, IL.


F53397 A  3/60 - "Compact Wall" or "Slimphone"
F53397 B  5/60

Uses Princess-style #8 dial and standard G3 handset.

Never mass produced but the form was similar to the 1554 TouchTone wall set that was later developed.

Stromberg Carlson (Comdial), ITT, AE and others did make a similar rotary "miniwall" set.

WE 701 Princess
1959 -- Princess set as announced -- 701B

Number 8 "compact" dial
External Ringer
External transformer for dial light
Night light switch on back

An optional lead weight was added after release to help keep the phone from sliding while dialing.

Shown with announcement-related premiums: mini sets and keychains.

November, 1962 -- 702B announced

Integrated a ringer into the base in place of the lead weight.

For details on models produced, go here: PRINCESS SETS
Princess Keyset
ca. 1960

Princess Keyset concept

Marked "Display Sample" - non-working

(Image courtesy of AT&T Archives and History Center, San Antonio.)
Use this link to the Touch Tone Princess Timeline
To Touch Tone Princess Development Timeline

Trimline development timeline -- announced in 1964
Design goal: Produce a set with the "Dial In Handset"

See "The Evolution Of A Telephone," Bell Laboratories Record, January 1966.

"From Butt Set to Beauty - The Trimline is 50 Years Old," Singing Wires (TCI), August 2015.
"Another Branch on the Trimline Family Tree," Singing Wires, May 2019.

D-type Test
                  Sets - 1920s-50s
1920s - D-Specification Type Handsets (Test Telephones)

Dial is positioned behind the receiver.

Used within the Bell System and by independents.

Components and construction vary by model variation.
    Some variations include:
        D-81760, D-81761, D-81762, D-81763


1926 - Y-3091 Hand Test

Y-3091 Proposed Machine Switching Lineman's Handset

Dial is positioned on the talking side of the hand test set.

For detailed photos and descriptions of this set and the D-Specification sets, see:
  "Another Branch on the Trimline Family Tree," Singing Wires, May 2019.

WE buttset concept
ca. 1934

Wood design model for a rotary lineman's test set.  Contains real transmitter and receiver elements, but a mock-up dial.

Final version, model 1011, first released in about 1939 is shown in the background.

Mentioned in the 25th anniversary press release as the inspiration and starting point for the "dial in handset" project.

One Piece
                  Dial-in-handset, 1952
(Photo from BLR, Jan 66, p 10.)

Design model with dial in handset.  The transmitter is in the center of the dial, so the user doesn't have t turn the handset around to dial.

One piece telephone with switch hook button on the bottom.  No ringer.

Also mentioned in the 1989 Trimline 25th anniversary press release.

DIH wood model
(Courtesy of Wayne Merit)
ca. 1955 - 1956

Numerous design concept models were made from wood.

Additional sets...

Demitasse in beige

F52578  8/57 - "Demitasse"

The Trimline's design goal was to put the dial in the handset while having a very small base.

Complex dial with transmitter in center.

There was also a wall mount for this handset:
F 58997 - "Demitasse" wall.

Trials in San Leandro, CA and Columbus, Ohio.  400 sets in each city.  Tested with Bedroom Set and Ericofon to determine customer preference for dial placement.

Separate trial in Brooklyn, NY.  150 business and residential customers.

Paystation with dial in
(From a Bell System future products chart)

Paystation with a dial-in-handset.
Ribbed fingerwheel
(Image courtesy of AT&T Archives and History Center, San Antonio.)
ca. 1958

"Display sample" -- wood model

Uses a ribbed fingerwheel, instead of one with holes.  This design failed miserably in user testing, as fingers kept sliding out when dialing.  The familiar holes were retained.
                    Dial-In-Handset prototype
WE Schmoo
(From Bell Telephone Magazine, Jan/Feb 1968, courtesy of Jonathan Sowers.)

F 53273  4/59, 6/59 - "Shmoo"
F 53635  5/60

Receiver and transmitter were sealed in handset.  Uses slots instead of holes over elements.

Base works on desk or wall.

Bulge in handset handle needed for dial.  Note the space between 0 and 1 holes.

Trials in New Brunswick, NJ.

WE Contour
                  dial set offhook
(From Bell Telephone Magazine, Jan/Feb 1968, courtesy of Jonathan Sowers.)
F 53751  10/60, 11/60 - "Contour"

Shaped like the "Shmoo" but narrower and slightly more compact.  Used the compact dial with moveable fingerstop that was announced with the Trimline as the #10 dial to reduce the width of the handle.

Trial in Richmond, VA, New Jersey and Pennsylvania.
Trimline Design
                  Model Wood Center FS
(Courtesy of Lucent.)

Wood design model

Early concept for a moving fingerstop dial to reduce dial size, eliminating the bulge in the center of the handset.  Note that the fingerstop is connected to the dial center.
Trimline wood model
(Courtesy of Wayne Merit)

Wood design model

Next generation, with the fingerstop in a more traditional position, along the rim of the fingerwheel.

The contours on the handset and base are slightly more angular than the previous version.
Dial In Handset Field
                  Trial Set

WE Dial-In-Handset
(1962 Bell System ad, "No end to Telephone Progress")

F 53751 12/60 - Trimline  ("Trimline I")
F 53754 10/60 marked inside handset.

Includes a prototype of the #10-style dial with moving fingerstop, and maintains the Shmoo-like horizontal vents for transmitter and receiver.

The pins on the cradle are shown in their projecting position, for use as a wall phone.  On the wood model above, they are shown retracted for desk use.

Trial in Richmond, VA. 
Carafe 1962

F 54523  6/62 - "Carafe" wall phone

Trimline-style, "space saver" dial with floating fingerwheel eliminates space between 0 and 1 holes.

Dial face can tilt and swivel.  Handset can be repositioned

Product Trial in Providence, R.I.

F-55580 desk

Trimline 1963 prototype
(Bell Telephone Magazine, Summer 1963)

F-55580  12/63 - "Dial-in-Handset," ("Trimline II"), desk set.
Field trial version of the Trimline.

There appear to be a few very minor differences compared to the final version, such as the added "recall" button and placement of fastening screws for the housing halves.  Note the return to holes instead of slots used in the Trimline I above, the shape of the plunger and the slight ridge above the transmmitter.

Product trial in 1963 in Royal Oak, MI, and market trials later in the year in Jackson, MI and Janesville, WI.  Jackson trial allotment was increased from 1500 to 1800 in December.  Trials lasted 6 months.

Available in black and all standard colors.

Trimline Field Trial Set
(BSP courtesy of the Pioneer Museum)

F-56093 - "Dial-in-Handset," ("Trimline II"), wall set.
Field trial version of the Trimline.

BSP 502-150-900PT, Issue A, April 1964.

Trimline rotary wall set
1964 -- Trimline set as announced

Smaller #10 dial with floating fingerwheel finally eliminated the bulge.

Production handsets were marked 220A inside the handset's back cover.

Bases were stocked seperately and mated with handsets at installation time.  Installers could then mix and match to get a rotary or TouchTone handset with a desk or wall base.

  AC1 - wall base (shown here)
  AD1 - desk base (see TouchTone page)

Wall base has a ridge to "park" the handset (shown).

Desk base is shown on the Touchtone model here.

Announced in the following colors (eventually available in all standard colors):

   Desk: beige, white, pink, blue and turquoise.
   Wall: beige, white, yellow and pink.
Use this link to the Touch Tone Trimline Timeline
To Touch Tone Trimline Development Timeline
Trimline Message Waiting Alternatives
(Courtesy of Lucent.)
Message Waiting

At least three alternatives were tested regarding location of a message waiting light for Trimline sets.

1.  Two lights -- one on each side of the base.

2.  In a cutout just above the handset cord on the handset.

3.  Part of the plug on the handset end of the handset cord.

Alternative 3 was chosen.  It eliminated custom cuts to the handset and base plastic and the associated inventory issues.  Having it in the cord also made it possible to easily add message waiting to any Trimline set equipped with a fifth conductor in the line cord jack.
2 line Trimline base
(Top 2 photos courtesy of Lucent.)

6 button Trimline base

Wall mount keyset base
(Courtesy of AT&T Archives and History Center, San Antonio.)
Trimline Keyset bases

2 lines and hold
     F 57226 12/67

6-button keyset (for 1A2)
     F 57728 12/67

Wall mount base
    F 57227  11/67

    (lacks key caps)

Other Rotary Models
Calculator-style dial

Calculator-style dial inside

- - - - - - - - - - -

Calculator Dial -
                  ca 1950
Set with later dial -- ca 1950 (BSTJ)
ca. 1940

Concept set with calculator-style dial for pre-set dialing

The idea was to make the dialing process faster by having the user set the number in the wheels and let the phone control the dialing rate, with no wasted time between digits. [Similar to the way we now enter a complete phone number in our cell phones and hit SEND.]

There are 7 large disks with pins along the edge, similar to some mechanical calculators of the day.  Windows along the top show the currently selected digit.  The first three have the appropriate 3 letter groups for exchange names instead of the digits 2-9.  (e.g. ABC instead of 2)

The coil and capacitor are mounted on the right side - dated 1940 and 1938.

The housing is heavy cast metal, similar to the housings of the metal 300-series sets made at about the same time.

The number was dialed when the handset was lifted.  A reset button on the front right allowed the user to cancel the preset number to correct an error or set a new number.

A number of similar sets, using the same housing were built into the mid-1950s, as part of a Bell Labs program to develop and test an experimental Electronically Controlled Automatic Switching System (ECSS). The goal was to test concepts that would minimize the holding time of central office resources by taking control of the dialing process away from the subscriber. The called number was pre-set using the levers, and the number was dialed using high-speed "pulse-position-dialing."

This was clearly a laboratory experiment, and the signaling process was totally incompatible with existing equipment. There was no intent to put this system in regular service. Several patents were issued in the early to mid 1950s.

Highlights of the system, including operational results, are included in the article, "An Experimental Electronically Controlled Automatic Switching System," Bell System Technical Journal, May, 1952, page 443. (Copy in the TCI LIbrary.) It's a very interesting read, if you are interested in switching systems.

The article shows a later dial design, replacing the status windows above the dial with letters and numbers on the disk edges. Also, an 8th digit was added for a party line code -- J, M, R and W.
Pull down dial
(Image courtesy of AT&T Archives and History Center, San Antonio.)
ca. 1940

Concept set

Cylindrical "pull down" dial designed by Clarence Lovell

Note the layout:
   8 9 0
   5 6 7
   2 3 4

Years after first seeing this photo I was able to research the project that created it plus a similar phone auctioned on eBay. Find the story in the three-part series titled "Why Build a Linear Rotary Dial?" in TCI's Singing Wires issues from March, April and May 2020.
WE distance talking set
("Seventy-five Years of Progress", SNET, 1953)

"Distant Talking" Wireless Phone (Speakerphone)
Fingertip set
(From The Reporter, July 1958)

"Fingertip" Executive Keyset

Trial held with 25 executives in Bell Labs' Murray Hill facility.

Included the 6-E Intercommunicating System.

Keys are for outside lines or for direct calling to frequently used internal extensions.  Includes speakerphone.
Desk Drawer Set

Desk Drawer Set

F 53530  2/60

Designed to be built into an executive's top side desk drawer.  His desk could be neat and tidy, yet the phone would be convenient, when needed.

This one includes a 6-button keyset, speakerphone and retractable handset cord.

There's another example in the Experimental Phones Display.
Wall Keyset
(Image courtesy of AT&T Archives and History Center, San Antonio.)

F 55341  9/62

Modified 554 to include a 6-key strip and exclusion.
Uses a single gong N-type ringer.

There are more details and photos of the inside of this interesting phone in the October 2014 issue of Singing Wires from Telephone Collectors International.

Back issues of Singing Wires are available on-line to TCI Members at:

While you're there, check out the September 2014 issue. TCI Member Jim Schultz modified a standard 554 wall set based on this photo and tells how he did it.

Info on TCI and how to join are found on their web site:

                  speakerphone control
(Bell System ad, "Tomorrow's Telephones." )

Capri with speaker
(Lower two images courtesy of AT&T Archives and History Center, San Antonio.)

Capri keyset

Speakerphone Control Unit ("Capri");

with speaker from a Bell System future products photo (mid),

and a "Display Sample" of the keyset configuration.  (bottom)

All require a small external speaker, suah as the model 758 shown.  The small switch on the front adjusts sensitivity for noisy environments.
Panel Phone Concept with
(Images courtesy of AT&T Archives and History Center, San Antonio.)

Panel Phone

WE panel phone prototype
(Bell System ad, "No End to Telephone Progress," 1962)

WE Panel and Prototype
(WE News, 2/65)
Panel Phones (Flush mounted to wall)

The first two photos are concept phones from about 1958.

The first includes speakerphone and multi-line features.


Panel Telephone Concept

The set on the right went to Field Trial with the number F-53324A.

The set on the left is the design that was produced as the model 750B.

Magnetic Dialer
(Image courtesy of AT&T Archives and History Center, San Antonio.)

Magnetic Dialer Telephone


50 number capacity.  Rotate the dial on the right to select number, lift receiver and hit "call" button.

4 buttons in lower right are:
  dial tone, reset, record (red) and call.

Field trial in Buffalo, NY.

Also found in a 1962 Bell System ad, "No End to Telephone Progress."
WE Executive Keyset
                  with Speakerphone

WE Executive
(Image courtesy of AT&T Archives and History Center, San Antonio.)

Executive Telephone with Speakerphone.

F 55076  9/62

Product trials in Chicago and Washington.

12 lines with hold and signal buttons.  Line keys could be associated with outside lines or for direct access to frequently called internal extensions.  Made in green, beige, gray and white.  Required Executive Interphone switching system control unit.
Never produced in volume.

There was also a shorter version without the speakerphone.  The cradle for the handset was across the dial, as on a Princess set.  This one is marked "Display Sample" and is non-working.
I'm looking for one!
What is this?
CGS Console -- Unmarked, ca. 1960, Light Gray

8 display lights with no apparent way to change the status.
            INC                ALERT          STA
  BUSY      READY      DA      OPR       RE ORD

White switch:  RESET, TALK, IDLE.

The dial is a fast (30pps) dial.

Matches Figure 16-2 Attendant's telephone set in "The Electronic Switching System, Trial Installation, Morris, Illinois, General Description" published April 1960 by Bell Telephone Laboratories, Inc.

Used for Attended CGS (Customer Group Services) to handle calls that are not completed automatically by direct inward dialing, or outgoing calls that require attendant services.

INC = Incoming from outside CGS,  ALERT = Action Required,  STA = New call from a CGS station or tie line, or a recall,

BUSY = Called CGS station is busy,  READY = CGS station formerly busy is now idle and can be connected,   DA = No Answer,  RE ORD = Try  again.

Calls are handled by entering codes using the rotary dial.

There are more details and photos of the inside of this interesting phone in the August 2012 issue of Singing Wires from Telephone Collectors International.
Wall keyset
(Image courtesy of AT&T Archives and History Center, San Antonio.)

Wall keyset

F56281  12-64

After a little contouring and a cradle redesign, this became the 851 set.

For. a predecessor set and info on the evolution of 500-type wall keysets, check out the F55341 above.
Other rotary models are shown here:
Tomorrow Calling Display
Continue to TouchTone models

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2005-2020 paulf.  All rights reserved.