Part 4 - Expanded Local Calling

1955 - Conversion to 7-Digit Dialing

Prior to 1955, you dialed 6 digits to reach all Atlanta numbers. Starting in 1955, in order to make long distance direct dialing possible, telephone numbers had to be converted to the 2L-5N system. This system used two letters, representing the office name, plus 5 digits.

Instead of just adding a digit to the existing office names, as you might have expected, They decided to give all of the offices new names. In central office buildings that had multiple office names, a single name was assigned and the multiple offices were differentiated by a number. For example, prior to the change the Decatur offices were Dearborn, Crescent, and Evergreen. After the change, there was only one office called "Drake" with 3 codes, Dearborn being replaced with "Drake 3", Crescent with "Drake 7", and Evergreen with "Drake 8". This was extremely confusing change for people. Especially since the change took place over a two year period in three parts.

First Cutover


The first cutover occurred on August 21, 1955, affecting part of the Downtown area, the West and East Point offices.

The Melrose Office

On the same day, the new Melrose central office was placed into service. The new office was located at Toco Hills on the northeast side. A portion of the areas served by the Midtown office, Buckhead office, and Decatur office were cut over to Melrose. The first Melrose codes were Melrose-4 and Melrose-6. Melrose was the city's last step-by-step office to be installed.

Second Cutover


The second cutover occurred on May 20th, 1956, affecting more of the Downtown offices, the Crescent avenue offices in midtown, and the Lakewood office, Dixie.

It is interesting to note that the name Jackson was reused. It had belonged to one of the Downtown offices from 1931 to 1946.

Walnut Panel Office Replaced

Southern Bell used this opportunity to replace the original Panel Switching machine that was installed in 1923. The machine had served the city well for over 32 years. The single Panel machine, in the Auburn Avenue building, serving the Walnut office was replaced by two newly installed No. 5 Crossbar machines in the 51 Ivy building. This was necessary because the traffic handling capacity of a single Panel machine was greater than that of a single No. 5 Crossbar. So during the number conversion, Walnut was split between the two Crossbar machines, each having its own code. The first 2500 numbers went to Jackson-1 on the first machine and the remaining 7500 numbers went to Jackson-2 on the second machine.

Final Cutover


The final cutover was done on November 18, 1956. Coinciding with the final cutover, another new central office, Butler was placed into service on the south side of Decatur on Columbia Drive. Several thousand customers served out of the Decatur's East Lake Drive offices (Dearborn, Crescent, and Evergreen) offices were cut over to the new office and given Butler-9 numbers.

During the 9 months between the first cutover and the last cutover, Atlanta telephone numbers were a mixture of 6 digit and 7 digits. Here are some telephone numbers before and after the big numbering change:

Rich's Department Store ….. Walnut 4636 became Jackson 2-4636
Grady Hospital Ambulance….. Cypress 4711 became Jackson 4-4711

Wrong Numbers

By 1957, the newly completed number changes were still causing a lot of confusion. For example, many people didn't know how to spell Sycamore and dialed "SI" or "CI".

Number 5 Crossbar


The No. 5 Crossbar System, which first entered service in 1948 in Media, Pennsylvania, used much of the same technology that was used in the 4A Crossbar toll machine. The machine was designed specifically to be used in suburban central offices. But it turned out to be such a flexible and successful design that it became Bell's all purpose central office machine. The No. 5 Crossbar machine had many advances in call handling capability, including the ability to select alternate routes when the primary route to a given destination was unavailable. The machine also took up less floor space than a comparable Panel or Step-by-Step machine.

Three new No. 5 Crossbar machines were placed into service in Atlanta on November 18, 1956, during part of the great renumbering. Two of the new machines were located in the newly expanded 51 Ivy building. These were given the codes Jackson-1 and Jackson-2. The third machine was placed in a new office called Butler on Columbia Drive in Decatur, with the initial code Butler-9.

The only drawback to the No. 5 Crossbar was its fixed switching matrix, which placed a limit on traffic handling capacity. In the Panel and Step-by-Step systems, any amount of traffic could be handled by adding more switching equipment. As a result of this limitation, a single No. 5 Crossbar machine could not be used to replace the Panel machine serving the Walnut office and two separate machines had to be used.

Dial Tones, Busy Signals and Ringback Tones

Tones were produced by a large motor-generator known as the ringing machine that also generated the ringing current to ring telephones. Early Atlanta central offices had ringing equipment that produced a ringing tone having a raspy sound. The smaller offices in the outer suburbs also had a similar sound.

At some point in the 1950s, the standard tones used for larger central offices were changed. This was part of a nationwide plan to make it easier for operators and test equipment to recognize the tones.

The new ringing tone was much more pleasant sounding, consisting of a combination of tones that had a musical quality. It has been called City Ring but there may never have been an official name. A unique characteristic of this ring sound was the static or "shhhh" sound between rings. This was caused by mercury drum interrupters. You would also sometimes hear background sounds, such as busy signals, in between rings. This was just a part of the soundscape of the telephone network at the time.

These sounds were generally the same throughout Atlanta and other cities throughout the U.S. but there were many subtle differences in the sound between offices.

Smaller central offices in outer metro area did not get new tones and continued to have a raspy sounding tone. Other types of tones were introduced in later years.

7 Digit Conversion for Outer Offices

To complete the 7-digit dialing plan for the metro area, Chamblee, Clarkston, and Smyrna were all given office names. Now they could be dialed without any special EAS access code. Prior to this the code "4" was required when calling those exchanges. The names chosen for the offices kept the initial "4" and the actual routing from the Atlanta offices did not change.


Calls placed from these offices back into Atlanta still required the single digit prefix. Clarkston and Chamblee customers dialed "8" first. Smyrna customers dialed "3" to call Atlanta. It is interesting to note that the name Hemlock was reused for Smyrna after it had been the name of the office on Crescent Avenue in Atlanta from 1915 to 1952.

Office Name Dialing Sequence from Atlanta Dialing Sequence To Atlanta
Clarkston Hickory-3 443-XXXX 8-XXX-XXXX
Smyrna Hemlock-5 435-XXXX 3-XXX-XXXX
Chamblee Glendale-7 457-XXXX 8-XXX-XXXX

New Sandy Springs and Ben Hill Offices

Two more No. 5 Crossbar offices were installed in 1957 and 1958. The new Sandy Springs central office, with the code "Blackburn-5" was opened in 1957. A large number of customers on the north side of Buckhead were changed to this office. Then in 1958, the Ben Hill office on the southwest side of town was opened with the code "Diamond-4".

1960 - The World's Largest Toll-Free Calling Area

In 1960 Extended Area service was expanded. Southern Bell called this "The Metropolitan Service Plan". 11 more offices in outlying areas were added to the local calling area. Another name for this service is "Extended Area Service" (EAS). The map shows the toll-free calling area. Solid lines represent free calls as of October 2, 1960. The dotted lines represent additional free calling added April 2, 1961.

This created the world's largest toll-free calling area. In larger cities, like New York, there were big local calling areas, but these were not free. They used a system called "message units", where you were billed on a meter, like with your electric service. You paid at least one 5 cent message unit per call. Calls to farther away points incurred multiple message units per call.


Dialing Extended Area Calls from Atlanta

One of the problems of providing service to such a large area was the number of central offices involved. By this time there were close to 20 central offices in the Atlanta Exchange and more than 20 offices in the extended area. Atlanta offices already had direct trunks between each other but it would not have been justified to have direct trunks from each of these to all 20 of the extended area offices.

It was also decided to avoid requiring Atlanta customers to dial special access codes to reach the outer areas. To do this, they assigned telephone numbers beginning with "4" or "9" for all of the outer offices. This allowed Atlanta Step-by-Step offices to route these calls to a tandem office on the first digit. Only the Step-by-Step offices needed this special numbering plan. Crossbar offices were able to route calls based on the first 3 digits via direct trunk or via the tandem without restriction.

There were two tandems in Atlanta at this time. There was a Step-by-Step tandem in the 51 Ivy building that had trunks to all of the outer offices. This was probably an expansion of the equipment that had been used up to this point for calls to Chamblee, Clarkston and Smyrna.

There was also a new Crossbar Tandem machine that had just been installed at 51 Ivy building to serve a combination of EAS local service and Direct Distance Dialing. This machine may have handled some of the Atlanta outgoing local traffic as well as the incoming traffic from the outer offices.

Dialing into Atlanta from Outer Offices

Most of the outer offices used Step-by-Step equipment. Calling from these offices back into Atlanta or to most places in the outer area required an access code. The most common code was "8". When you dialed "8", this connected you to the Atlanta Tandem. This would have most likely been the new Crossbar Tandem in the 51 Ivy building. After the "8", you dialed the 7 digit number into the tandem, which completed the call to the destination office.

Direct trunks were provided to neighboring offices only. For example, if you were in Clarkston, you could call Clarkston numbers, Stone Mountain numbers, and Chamblee numbers by just dialing the telephone number. But to call Atlanta or any other town in the local calling area you had to dial "8" first, followed by the number. In each of the outer offices, the Atlanta access code might be different and the list of offices that you could call without the access code varied. So you had to check the telephone directory before dialing from an unfamiliar place.

If you were lucky enough to be served by an office that had No. 5 Crossbar equipment, you did not have to dial any special digits and you could call any number by dialing only 7 digits. At this time, Roswell, Austell and Jonesboro had Crossbar equipment.

Some of the offices that became local to Atlanta were quite a distance from the city. To save on cable pairs required, carrier equipment was used. Carrier equipment allows multiple conversations to be multiplexed over a single pair of wires and allows for amplification of signals along the way. Carrier equipment was even more important in the long distance network. On long distance circuits, special care was taken to make sure the transmission was high quality and as balanced and quiet as possible. Both local and long distance carrier circuits used a form of signaling known as Single Frequency (SF). This used a high pitched tone, usually 2600HZ, to signal that the called party had not yet answered.

Less attention was paid to the quality of carrier systems used in the local calling area. As a result, some of these circuits were much more noisy than long distance circuits to much more distant places.

To add further to the distance, some calls had to go from an outer office, through Downtown, and back out to another outer office.

The following is a recording of a complete call from a Stone Mountain 476 number to a Buckhead 233 number. The caller dials 8 first, followed by the 7 digit number. You will hear the sound of the connection to the Decatur tandem come on when the initial 8 is dialed. After the rest of the number is dialed, there is a delay, followed by the tandem connecting through to Buckhead and the number ringing. This would be typical of the sound of these circuits during this time period.

Retirement of Panel Switching

The city's only remaining Panel switching machine was removed from service in 1960. This machine had been placed into service in the Auburn Avenue building in 1928 to serve the Main office. In 1955, Main was changed to Murray-8. Now, in 1960, a new Number 5 Crossbar machine in the 51 Ivy Building took over the Murray-8 Office and the panel machine was retired.

All Number Calling


1960 was the start of conversion to "All Number Calling" (ANC). The telephone company stopped giving names to new offices and referred to them by numbers only. Eventually the names were dropped for the offices that previously had names. In the 1960 telephone directory, new subscribers added in the past year showed all numbers. Customers that had had service prior to 1960 were listed with the office name abbreviated to two letters, followed by 5 digits. This practice continued until 1963 when the directory listed numbers only.

New Offices

Two new offices were opened this year. The Woodland office was opened on Woodland Avenue serving a northwest section of town using the "355" code. The same year, the Forest Park Office was opened as "366".

Further Expansion of Metro Calling

In April of 1961, four more communities were added to the metro calling area. Alpharetta, Conyers, Palmetto, and Powder Springs could now be called.

In 1962, a new central office was opened in Tucker. The Tucker office took over a portion of the area previously covered by the Clarkston, Chamblee, and Norcross offices and immediately became part of the Atlanta local calling area. The first code there was "938". Southern Bell conducted an open house, inviting the community to take a look at the new No. 5 Crossbar equipment.

Next, in 1963, the Marietta office was expanded and a new No. 5 Crossbar machine was added, serving the "422" and "424" codes. This machine had a rather strange setup. You can read about it in the Central Offices section.

Acworth and Woodstock on the Northwest side and Hampton, McDonough, and Locust Grove to the Southeast were added to the metro calling area in 1963.

Finally, in 1964, Dallas to the Northwest, and Lawrenceville and Buford to the Northeast were added. This created the largest toll-free dialing area in the world.

Dialing instructions for some of the outer Step-by-Step offices became rather complicated. For example, these instructions were printed in the Marietta telephone directory in 1964.

TO CALL Marietta 422, 424, 427, and 428 numbers,
Smyrna 435, and 436 numbers, Dallas 445 numbers,
Woodstock 926 numbers, Austell 948 numbers,
Douglasville 942 numbers, Powder Springs 943 numbers,
and Ackworth 974 numbers …… dial the 7 digit number.
TO CALL all other Metro Atlanta calls …… dial "6" plus the 7 digit number.

Another really complicated one was Chamblee.

TO CALL 451, 457 (Chamblee), 938, 938 (Tucker)
and 993 (Roswell) numbers ….. DIAL the number desired
TO CALL 443 (Clarkson) numbers ….. DIAL "3" plus the number desired
TO CALL 476 (Duluth) numbers …… DIAL "5" plus the number desired
TO CALL 448 (Norcross) numbers ….. DIAL "9" plus the number desired
TO CALL Atlanta and all other places shown
on map on opposite page ….. DIAL "8" plus the number desired

Information and Repair Service Codes

In 1964, the access codes were 113 for Information (Directory Assistance) and 114 for Repair Service. Since Marietta had its own Information operators, it was necessary to dial 42-113 for Marietta listings as well as Powder Springs, Acworth, Austell, Dallas, Douglasville, Smyrna, and Woodstock.

The Trimline phone was also introduced this year.

Decatur Crossbar Tandem

In 1964, the Decatur Crossbar Tandem was opened. This machine was the same type as the one installed in 1960 downtown. But this one was placed into service to handle the increasingly complex traffic of local calls in the large Atlanta extended calling area.

When calling from the outer suburban Step-by-Step offices to other metro numbers, you dialed an access code (usually "8") first. These calls had to be handled by a tandem machine of some type. The crossbar tandem was ideally suited for this job. In addition to switching the calls to the appropriate office, it was able to provide Code Screening.

Here is an example of a call from a No. 5 Crossbar office in Atlanta, going through the Decatur Crossbar Tandem. You can hear the clicks of the dial pulse signaling from the tandem to a Step-by-Step destination office.


Here is another example where the Decatur Crossbar Tandem is sending multifrequency pulsing (MF) to the destination office, which is another No. 5 Crossbar.


Dialing Extended Area Calls into Atlanta from Outer Offices

Code Screening was used to prevent customers from dialing calls incorrectly by using an "8" when it wasn't needed. Doing so tied up trunks to the tandem unnecessarily. For example, if you were in Lithonia and needed to call Conyers, your instructions were to dial only the 7-digit number. This was because the Lithonia office had direct trunks to Conyers. If you needed to call Tucker, however, you had to dial "8" plus the number. Since Lithonia had no direct trunks to Tucker, dialing "8" connected you to the Decatur Crossbar Tandem. The tandem then connected your call to Tucker. Since most area offices required "8", you might have forgotten that you didn't need to use it to call Conyers. If you dialed a Conyers call with an "8" first, it would have gone through without any problem except that it would have tied up a more expensive trunk to Decatur and another more expensive trunk from Decatur to Conyers. Code Screening in the tandem would block this call. It had the necessary information wired into it to know that it was not permitted to route calls coming in from the Lithonia office going to the Conyers office.

Prior to the installation of this machine, calls from most intown offices to the outer suburbs went through the downtown Step-by-Step tandem or possibly the downtown crossbar tandem.

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