When Letters Were Added to Telephone Rotary Dials

When dial telephones began to be replaced with automatic exchange systems, letters were added above digits. Except for 0 which was reserved for Operator, every other number sported three letters above it.

Today, rotary phones still work on most networks but they’re being replaced by touch-tone ones that use audio tones outside of the frequency of human speech and interact well with automated voicemails. So, when letters were added to telephone rotary dials, which word could not have been spelled out? and which word could not hav?

1. 0

When rotary dial telephones were first introduced they often sported letters above the numbers, as shown in this 1952 instructional booklet. With your finger in the digit hole, you turned the dial clockwise, stopping it at the next letter, then releasing it to let the dial spin counter-clockwise back to its rest position.

You then repeated this sequence for each digit, using the letters to help you remember the number. As the phone numbering system expanded, so did the use of letters, and the number 0 was reserved for calling the operator.

Later, as all-figure dialing was rolled out, the letters were gradually phased out (except for 0). This arrangement was also used on some phones made for New Zealand, which shared the same phone exchange equipment as Britain, so it’s not surprising that dials exported from there would occasionally end up on British telephones. The North American letter arrangement was omitted on these, so digit 6 carried the letter MNO.

2. 2

In North America, traditional dials used an associative lettering arrangement on the finger wheel, which allowed a caller to easily reach named exchanges. This lettering was later replaced by the numbers 0 through 9. It also made it easier to memorize telephone numbers.

The letter arrangement was carried on the faceplate and rotary fingers of some telephones (such as this 1931 Ericsson) that remained popular in Europe. Another example of the letter arrangement can be found on a BPO No. 10 dial supplied by Siemens Bros. for a telephone company in Manitoba, Canada.

Until the 1960s, rotary phones replaced operator-assisted ones and there were still instructions for people to follow to use them. This basic set of instructions was printed in a 1952 telephone book:

3. 3

Users such as Violette claim they want to keep their rotary phones because it’s like having a piece of history. They also say they’re a good backup plan in case cellphone batteries die. Another user, Talmort O’Dole, suggests rotary phones are more sturdy than cell phones and could be used to defend against an intruder.

As the fingerwheel is rotated, it generates a series of pulses on the telephone line that correspond to the position of the dial. The pulses interrupt the current and are transmitted to the central office, which then sends a call to the destination number.

Rotary dials had no redial feature, so it was essential to have the complete phone number memorized. If a mistake was made in dialing, the customer must hang up, wait for a moment and then redial the entire number to reach a live operator. The operator must also be notified of the error, so that a correct bill is issued.

4. 4

When you rang someone on an old rotary telephone, you stuck your finger in a hole in the dial and spun it in a clockwise direction, producing a satisfying “zzzzztt!” noise. When it stopped, you removed your finger and let the dial spin counterclockwise back to its resting position. Then you started all over again for the next number.

Since early phone numbers contained both exchange names and digits, dials soon sported letters above the numerals. For example, Pennsylvania 6-5000 was dialed as PE-5000. Later, the letters were omitted from the dial (and the letter Q was omitted from the code) except for 1 and 0, allowing more than one digit to be dialed before reaching the operator.

Today, we touch-tone dial our contacts list to memorize them so we don’t have to think about the digits. But those days when phones were still rotary dials, mapping digits to letters made it easy for people to remember and recall them.

5. 5

During the heyday of the rotary dial, people who used to work at telephone exchanges would have to memorize phone numbers and their associated names. A standardized letter arrangement helped with this process by making it easier to map a number to an easily recalled phrase.

With a rotary dial, you placed your finger in the hole of the ring and spun the dial clockwise (while listening for the “zzzzzt” sound that accompanied the pulsing action of electro-mechanical relays). When the dial reached its rest position, the ratchet moved contacts and opened an electrical circuit. That in turn sent the number to a human operator in a central office. Once that number had been passed to the operator, it was transmitted from there through the wires of a telephone network to the destination. The whole process could take a while, especially if the number was long and required several digits to complete.

6. 6

When rotary dial phones first replaced operator-assisted calls, it was possible to have an entire alphabet associated with each digit. This aided human operators who didn’t have perfect memories, or even a way to look at numbers.

It also facilitated memorization, and sped up calling by eliminating the need for finger-wheel rotations. The letters also helped distinguish one number from another in a busy office, as the number would be spelled out for the operator.

This arrangement was maintained until it became necessary to allow international direct dialling. To do this the letter Q was moved from digit zero to digit 7. It is still found on dials supplied by Siemens Bros. to telephones for their UK customers. Other letters are omitted on this type of dial. It was later used on push button phones in two locations in Britain. This layout was also adopted on dials for the network in Guernsey.

7. 8

Many rotary dials had letters associated with the numbers (not pictured here) on their faceplates. These correlated to the number of pulses that each digit needed to signal the switchboard, and different encoding systems used different letter codes (one pulse for zero, ten for nine).

Early area code maps were drawn up by calculating the total number of pulses required to dial a particular number. Digits 8-9, which needed more pulses than lower digits, were given to cities with heavier population densities, while 0 went to sparsely populated areas.

While touch-tone phones have replaced rotary phones, the old-school models are still making a comeback—in places like homes, offices and bars. Some even use them as alarm clocks. Regardless of their practicality, these phones are a cool piece of history that could be worth a look if you have one sitting around. But just be careful with the knob: They’re heavy, solid and can hurt your fingers.

8. 9

When we dial a number today, we do it without even looking at the digits. But when you rang up a phone in the ’70s, you had to look at the dial and match each letter to some meaningful, easy-to-remember phrase.

As telephone numbers grew, so did concerns that consumers wouldn’t be able to remember all the different when letters were added to telephone rotary dials, which word could not have been spelled out?. So each of the holes in a rotary dial was assigned three letters (except 0 and 9), from A to Z, with a separate pattern for each number: 1 ABC 2, DEF 3, GHI 4, JKL 5, MNO 6, PRS 7, TUV 8, WXY 9.

This system eventually disappeared when all-figure numbers replaced letter codes and push button phones, such as AT&T’s Touch-Tone, made their way to the market. However, rotary phones were still produced for some time, until they too were finally supplanted by DTMF dialing with keypads. A growing generation is growing up that will never know the joy of putting your finger in a phone rotary hole and spinning it clockwise, producing a pleasing “zzzztt!” sound as it came to a stop.


When a rotary phone user rotated the dial with their finger, each revolution sent different numbers of pulses to the exchange. For example, dialing a number with a 7 in it required seven rotations of the dial. Those pulses were then used to connect the caller with their desired party.

During the period of time when rotary dialing replaced operator-assisted calling, this basic instruction was printed in many telephone books.

Despite the rotary phone’s relatively short lifespan, it still holds an odd place in the heart of many. As vinyl records and independent bookstores make a comeback against digital competitors, some believe the rotary phone will follow suit. Its retro look is appealing and it can even be used as a weapon in the event of an intruder. In addition, a rotary phone is more durable than many modern devices and can function as a flashlight during power outages. For these reasons, one user named Talmort O’Dole recommends keeping a rotary phone as a backup to your smartphone.