When Was the Rotary Phone Invented


The charm of picking up a phone and talking to an operator to dial a number has been part of Hollywood lore for many years. The only problem with this is the fact that the rotary phone, which allows for specific number dialing through a series of pulses that are controlled by a user dial, has been around since 1904. The first actual rotary phone patent dates back even further, having been invented by John and Charles Erickson, and their partner A.E. Keith, in 1896. It wasn’t until 1919, however, that the first rotary dial entered into service.

This trio worked for a company named Almon Strowger. This organization helped to modernize the modern telephone system with a number of key inventions. Here is a look at some of the highlights of their overall work.

1. The Automatic Telephone Exchange

Having an operator manually connect a phone line from one user station to another user station is not an efficient way to make a phone call, although it was used for quite some time. What makes this such a curious phenomenon is that Almon Strowger invented the automatic telephone exchange that was essentially a forerunner to the modern system that was employed for decades in 1889. By picking up the phone, a user could automatically connect to another telephone in order to speak with someone.

2. Improved Power Reception

Many of the early telephones needed a number of different wires to help them operate. Instead of the modern system where there is power that is connected through the phone line itself, the old telephones had multiple lines that were required to give power to the unit. This included a current reversal line. Almon Strowger invented a switching mechanism that would allow fewer lines into the telephone because it could switch the lines through electromagnetic switches installed on each line.

3. Permutation Selection

One you type a key on an old typewriter, the corresponding letter stamp comes up and hits the paper. It’s the same principle that allows for a specific key to be hit on a keyboard to have that letter show up on a computer. In terms of using a telephone, Almon Strowger invented a selection process through permutation that would allow each individual key to be assigned to an individual function that could be recognized on a telephone. This invention became the foundation of the rotary dial. Here’s a fun fact: the first rotary dialing mechanisms for a phone from this patent actually look like a typewriter.

4. Disconnection

Under the old system of telephone calling, the two user stations would need to be manually disconnected for the call to stop. This meant that it was possible in old versions of the phone to hang up the receiver and still be connected. The disconnection technology was developed by Almon Strowger so that the operator could automatically know that the lines were disconnected and respond accordingly. In return, power consumption could be minimized and the phones could be used for a new phone call almost immediately.

Evolution of the Phone