Interesting 4H dial detail

[poplar1]

In 1952, Los Angeles had a mixture of  2 Letters + 4 numbers and 2 letters + 5 numbers.

Unfortunately, this list includes only those C.O. names that were in the photographed pages of the ebay listing:
http://www.classicrotaryphones.com/forum/index.php?topic=9430.msg100912#msg100912

[Russ Kirk]

I don't mean to nitpick,  but I just want to clarify some terminology.

A Central Office (CO) is usually the physical building where dial tone is generated. 
Examples are:Los Angeles (LSANCA01, LSANCA02 and LSANCA03)

An Exchange in located within the CO. 
Examples are: ADams 1, HOllywood 9 or CApitol 2.
I think each Exchange is served by a separate switch.
(modern Exchanges use the three digit prefix code)

A CO may contain one or more exchanges. 

Please take a look at the following link. It will show some of the current COs and the Exchanges served by that CO.

http://www.thecentraloffice.com/Calif/LA/LAP/LAP.htm

[poplar1]

Yes, that website uses "central office" to refer to a building -- now often called a "wire center" -- and "exchange" for each group of 10,000 lines in that building (Atlantic 1, 2, 4, etc.)

However, that's not the way I heard it. An "exchange" is a geographical area that can contain one or more wire centers (buildings), and each building can contain one or more "central offices" of 10,000 lines each, sometimes called just "offices."

"Exchange" is often incorrectly used, as at the website cited, as well as the "Telephone Exchange Name Project," to refer to  one 10,000 line block. Comp.dcom.telecom and other groups call the first three numbers after the NPA (area code) "prefixes" or "NNXs" (now "NXXs").

[poplar1]

Here is an example from the BellSouth tariff for Foreign Exchange and Foreign Central Office service.
-----------------------------------------------------------------------------------------

A9. FOREIGN EXCHANGE SERVICE AND FOREIGN CENTRAL OFFICE SERVICE
A9.1 Foreign Exchange Service
A9.1.1 General Description
A. Foreign Exchange service is exchange service furnished to a subscriber from an exchange other than the one from which the
subscriber would normally be served, allowing subscribers to have local presence and two-way communications in an
exchange different from their own.

A9.2 Foreign Central Office Service
A9.2.1 General Description
A. Foreign Central Office service is an exchange service furnished to a subscriber in a multi-office exchange from a central office other than the one from which the subscriber would normally be served.


http://cpr.bellsouth.com/pdf/ga/g009.pdf

-------------------------------------------------------------------------------------------
You could actually order an FX line -- served by a different exchange, for example from another city, -- or an FCO line, which was from a different central office in the same exchange.

An FX line would allow potential Atlanta customers, for example, to reach a car dealer in Griffin, which at the time was a long distance call, without incurring toll charges, by furnishing an Atlanta FX line at the Griffin dealership.

We often ordered FCO lines when we didn't have enough customers to justify creating a new Centrex group. You have to pay "mileage" to get the dial tone to your local central office, but for Centrex, it was often cheaper to pay the mileage on top of a $10 charge for a Centrex line, rather than pay $60 for a 1FB flat rate business line.

[unbeldi]

I certainly have seen various differing usages for the terms exchange and central office too.

I don't think it is useful to call one or the other usage wrong, without providing a larger framework within which they are used. The terms have certainly changed meaning slightly over time as technology has changed and as the legal definitions have changed and the relationships between carriers has been revised.

The technical changes resulting from number portability certainly have removed the physical restrictions of the term exchange to a single building or single central office, and the providing of Foreign Exchange Service is or will only be history.

Clayton's Illustrated Telecom Dictionary (McGraw-Hill, 2000) defines the terms as follows:

central office
A building that houses a telecommunications switching
or trafficking system. Typical switching systems installed in
central offices in North America are Lucent Technologies' 5ESS and
Northern Telecom's DMS family of switches. There are five classes of
central offices and five major parts to a central office. As a whole these
parts are referred to as inside plant.

exchange
The area that a single central office services. Soon, when
number portability is fully implemented, an exchange will not be associated
with a central office. It will be associated with an area and the
legal regulations imposed on communications companies in that area.
Currently, each central office is assigned a group of numbers that it can
use. The numbers are the first three digits (not including the area
code).

exchange area
An area served by multiple communications companies
and multiple central offices. Each exchange area has its own legal regulations
regarding how companies can compete (or price and package
their services) and what services they are required to provide.

wire center
A reference to a telephone company central office's geographical
service area. The central office serves the area that its telephone
wires (outside plant) reach to.

It seems to me these definition permit the assumption that an exchange may well be a subset (a single switching system) of a central office, servicing only one particular area of all the areas the C.O. services. The definition however, assigns the three-digit prefix to the central office, not the exchange. I am not sure the distinction is meaningful though in this wording, because once a prefix is assigned to an exchange is is also assigned to a C.O. in historical framework before number portability.

In many publication one finds no distinction between central office name and exchange name, or central office prefix and exchange prefix, and in many if not most places, where there was only one local prefix/exchange, the difference was meaningless.

[unbeldi]

In Introduction to Telecommunications Network Engineering (T. Anttalainen, Artech House, 2003) the author writes:

2.6.3 Switching Hierarchy
During the early years of the telephone, the switching office or exchange was
located at a central point in a service area and it provided switched connections
for all subscribers in that area. Hence, switching offices are still often
referred to as central offices.

[unbeldi]

The work Engineering and Operations in the Bell System (BTL, 1984) shows these definitions in the Glossary section:

Central Office
Usually used to refer to a LOCAL SWITCHING SYSTEM that connects
LINES to lines and lines to TRUNKS. It may be more generally
applied to any network switching system. The term is sometimes used
loosely to refer to a telephone company building in which a SWITCHING
SYSTEM is located and to include other EQUIPMENT (such as transmission
system terminals) that may be located in such a building.

Central Office Code
A 3-digit identification under which up to 10,000
station numbers are subgrouped. EXCHANGE AREA boundaries are associated
with the central office code, which accordingly has billing
significance. Several central office codes may be served by a CENTRAL
OFFICE.

Exchange Area
Traditionally, an area within which there is a single uniform
set of charges for telephone service. An exchange area may be
served by a number of CENTRAL OFFICES. A call between any two points
within an exchange area is a local call.

[unbeldi]

Notes on the Network (AT&T, 1968) seems to find no distinction between central office name and exchange name:

9. CENTRAL OFFICE NAMES
9.01 In view of the conversion to All-Number Calling (ANC), all newly established central
office codes should be in ANC form.



The 1955 issue of the same publication (AT&T, 1955, Notes on Nationwide Dialing) also calls the exchange names as central office names (Section 9 and Appendix A).


The 1997 issue of this publication (BellCore, 1997, Notes on the Network) has this to say in the Glossary:

Central office
This term is usually used to refer to a local switching system that connects
lines and trunks. Sometimes it is used to refer to a telephone company building in which
switching system and telephone equipment are installed.

Wire center
The location of one or more local switching systems. A point at which
customers' loops converge.

Local Access and Transport Area (LATA)
LATA has been adopted to identify the
decree-prescribed "exchange areas" per the plan of reorganization.

(no mention of the term exchange)

[unbeldi]

Back to telephone issues....

I finally got the transmitter cap off the handset. Took a couple days soaking the threads with cleaner and then some force.

Surprise! There was a T1 transmitter hidden with proper centering rings like in the F4 handset.

Handset: F1  "61"(June 1951)
TX: T1 29 10-51 354T with 2 plastic rings
RX: HC3HC-5  5-53 (silver ink) 354 (vermillion) with brass ring
cord: H3AD IV-50

Since both, RX and TX, have matching refurb dates of March 1954, it appears original and intended to gain more efficiency. The customer must have been on a long loop.
So, this appears as an early version of the F4, it seems. I thought the F4 handset appears in fall of 1955, with T1 and U1 elements. The F4A and F4B show up in BSP C32.203 i7 5410, but with a U1 receiver, not an HC5.

BSP Section C32.275 Issue 7 5612 says this under F4/F5 transmitters (5.10) 
Transmission complaints in the past have been remedied by replacing the HA1 receiver unit with an HC5 receiver unit on F1- and F2-tvpe handsets. If an HC5 receiver unit is not readily available, replace the Fl- or F2-type handset with an F4- or F5-type handset, respectively.
When it is necessary to replace the F1 transmitter unit, replace with a T1 transmitter unit and two 18A529 rings (the contact springs in the handle should be adjusted, if necessary, to insure satisfactory contact with the T1 transmitter unit) or replace handset with a new F4- or F5-type handset.


I also received an email last night stating that the phone was in fact found at a house in Inglewood, CA.

[poplar1]

Compiled from info shown in BSP Section C32.275:  Issue 5 (4/54), Issue 7 (12/56) and Addendum Issue 1 (9/54):

Handset     Handle     Xmtr Unit       Rec Unit             
   Type 

F1               F1              F1             HA1 or HC5         

F4 (old)       F4              F1*            U1                      Iss. 5 (4/54) and Addendum Iss. 1 (9/54)
F4 (new)      F4              T1             U1                      Addendum Iss. 1 (9/54)

BA            ?  F1              T1             HC5

*only units newly made, or refilled, after February 1953 (stabilized carbon). Refilled units are marked "R."   

So your handset -- with T1 transmitter and HC5 receiver -- appears to be a BA-760726, rather than an F4A. F4-type handsets always had U1 receivers. 

[unbeldi]

Ah, thank you.   Very good. I don't have issue 5 of that BSP, but I do have the addendum which I overlooked. The addendum list this BA type handset.
Very interesting.  It says:  "Use the BA-type handset only if they are available from the distributing house or field stocks."

So, this means they actually stocked that parts combination, and it wasn't just something a technician put together in the field to solve a customer complaint.
This is the first time I have become consciously aware of this type of handset, but now I do remember seeing this table before, and wondering about the BA.

Amazing, that an old ugly-looking $27 phone, almost a spur of the moment buy, can teach so much, in addition to providing a 4H dial with an interesting feature.  Someone wants $125 BIN for a 4H on eBay, and the last auction went from $0.99 to $99 without meeting the reserve, so more than one considered it worth at least $90-some.  I actually only bought it because it had a 4H dial and it looked like it came directly out of  someone's basement, not from a "restorer". And the price was right.

The handset works very nicely, btw., It is markedly louder in both directions, transmit and receive.
From what I read, I would call this BA-760726 as an early F4, if I had to explain it, or the forerunner of the F4. Both the BA and the F4 replaced the F1G handset.  The F4 uses a special handle to accommodate the U1 receiver, while the BA uses the unmodified F1 handle with adapter rings.

Ok,..... now I see that I actually do have Issue 5 as well.  The file was mislabeled by the issue number of the addendum.  A common affliction of files from the TCI library, poor labeling.

So, we've learned something about 4H dials, about handsets, about number cards, and about exchange names and central offices. Also about Inglewood, Ca.

Thanks David, I am glad I posted about this find.

[unbeldi]

BTW, both rubber cords have dates that update the date charts for WE parts, if I am reading the charts correctly.

H3AD IV-50
D4AN 52   (no quarter)

[unbeldi]

I suppose a view of the phone for posterity might be in order, if not for beauty.
449

[Sargeguy]

I received a 4H dial the other day that had the shroud.  It is an unconverted "pure" 4H dated I 32.  It has no telco or refurb markings, but someone did put shellac? over the markings and some of the holes in the housing.

[unbeldi]

I received a 4H dial the other day that had the shroud.  It is an unconverted "pure" 4H dated I 32.  It has no telco or refurb markings, but someone did put shellac? over the markings and some of the holes in the housing.

Thanks... Interesting.  There is still more to be learned about these shrouds, I believe.
Does your dial still have the original single-point contacts, or has it been upgraded to twin-type springs? (I suspect not, but let me ask the question).
Sounds like it may have been refurbished without markings.