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This page displays photos of 1948, 49 and 50 -dated components submitted by collectors. Based on documentation found to date, sets are grouped as follows: Pre-production sets -- made in 1948 or earlier. Early Production sets -- made in 1949, some used in the 1949 field trial. Production sets -- made in 1950 and later. So far, we have photos of only one pre-production set and have info on only a few 1949 sets. There are probably more variations that were made that are yet to be discovered. This page is a work in progress. Please send comments, additions and corrections. Photos: D177001 by Dan Robinson, 1949 set in the Museum of Communications (Seattle) by Greg Goebel. Last update: 06 Aug 2010 |
| Base |
|
1948
Base (D177001 - Pre-production)
 |
|
1949
Base (Early Production)
 1950 Base (Production)  Cutouts in dial mount are to
hold terminal strips for optional future features.
Similar slots in the hookswitch mount are for an exclusion switch mount. These greatly increase the flexibility of the set, reducing inventory and making it possible to easily convert from one model to another during refurb. |
| Bottom
Plate |
|
1948
Bottom (D177001 - Pre-production)
 |
|
1949
Bottom (Early Production)
Drilled for mounting future options: tube for party line ringing, and line switch for 2-line version. Rivited feet.  1950 Bottom (Production)  Model number added and date
format simplified.
|
| Dial |
|
1948
D-177008 Dial (D177001 set - Pre-production)
  Included an inspection "window" on the front to watch the gear in motion. Eliminated before production.   |
|
1949
(Early Production) and 1950 (Production) 7A Dials were the same,
including the "Operator" text circling the 0 digit on the dial plate.  Dial components were
rearranged,
probably
to make the footprint small enough to use the same subassembly in the
3-inch
#6 dial, which was introduced after the #7 dial.
|
|
The 3" 6A dial (4-54) and the 4"
7A dial (4-53) apparently use the same gear arrangement.
(Differences are due to the slightly different camera angles.) Casting and contact subassemblies are obviously different.  |
| Housing |
| 1948
Housing (Pre-production) [Photo Wanted] |
1949
(Early Production) and 1950 (Production) housings were the same. Circular stiffener in lower right is for a hole for the (future) line switch. Switchhook plungers were changed from clear to black. |
| Ringer | |
1948
D-177006 Ringer (D177001 set - Pre-production) Note: Only 1 screw attachment point - changed to two (below). |
|
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1949
C2A Ringer
(Early Production)
|
1950
C2A Ringer
(Production)
 |
| Three
grommet ringer supports pressed into base were replaced by 2 captive
grommets |
|
| Equalizer | |
1948
D-177018 Equalizer (D177001 set - Pre-production) |
Internal
Equalizer Components. |
|
1949
(Early Production) and 1950 (Production) 311A Equalizers were the same
 (Bill Geurts photo) |
|
| Varistor
screw attachment to can was eliminated. |
|
| References | |
|
Date
Source* Topic
49/02 IB News 500 coming “Leak” – “still in design stage” 49/03/16 BTL Press Release – New Telephone Instrument 49/04 NE TelTopics - New Telephone Instrument, p 15 49/05 BLR - New Telephone Instrument 49/05 IB News - New Telephone Instrument 49/05 PacTel Mag - New Telephone Instrument 49/05 BTL Notes on Discussion at the Conference of BS Lecturers 49/06 Popular Science New Phone Rings Loud or Soft, p 108. 49/12/12 Life Mag New Telephone, p. 67 (also see p. 128 Dooner, yellow) 49/12/29 News Letter Field Trial in St. Louis (AT&T Archive) 50/02 BLR Cover Photo (Pre-production set) 51/01 BSTJ “The Ring Armature Telephone Receiver,” p 110 51/04 BSTJ “75 Years of the Telephone,” p215 51/04 BSTJ “An Improved Telephone Set” (500), p 239 Trials, 48 & 49, pre-production sets, 4000 in 49 51/aut BTM “A New Telephone” (500), p 164 52/05 BLR “Dial for 500 Type Telephone Set” (7A), p 211 53/03 Ohio Bell 510 in production, p 42 53/05 BSTJ “An Improved Circuit for the Telephone Set” (425B net), p 611 54/03 WE Mag p.7 (Manufacturing Locations) 55/sum BTM "Designing the Telephone" (from Dreyfuss book) Designing for People, Henry Dreyfuss, 2003, pp 106-7. Old Time Telephones, Ralph Meyer, 2005, p 88, p121 (dialing dots). Singing Wires, Jan - Aug 2009, Series on 500-series history. Singing Wires, Nov 2004, Henry Dreyfuss. * Source Abbreviations: BLR - Bell Laboratories Record BSTJ - Bell System Technical Journal BTM - Bell Telephone Magazine Other sources are Bell System press releases and employee magazines. e.g. IB - Illinois Bell, NE - New England Tel, WE - Western Electric Date format: YY/MM/DD, or YY/season |
