To dial a telephone number, you put your finger in a disc with holes in it, right? Well, actually no, not always. Although the rotary dial for automatic telephony developed into a disc with holes very quickly, there are of course other solutions to the question of making a device that generates pulses to signal to a telephone exchange. Because that is what most of these dials do, generate pulses on the telephone line.
All electro-mechanical devices used some kind of rotational motion to generate these pulses. Something had to turn to make the little clicks on the telephone line. It was not until the arrival of the electronic push button dial that a rotationless device appeared.
And now, in our smartphone era, numbers are dialed by touching a glass panel or even by uttering a voice command. The days of putting your finger in a hole to dial a number are gone.
So here is a small selection of odd dials from my collection, to remind you of how dialing used to be done: by sticking your finger into something instead of stroking a smooth surface.
Clicking sounds, calling numbers; how does that work?
Maybe you have heared it on a telephone, clicking sounds when you dial a number. Because that is how it used to work, by sending clicks to the exchange.
Even in the days of manual telephony subscribers found each other by number, rather than by name. The dial translates these number into clicks or pulses and sends them to the exchange. And the exchange finds the correct telephone line of the desired party.
A turning motion seems to be the most efficient method to generate these clicks at precise regular intervals. All electromechanical dials use some kind of turning mechanism to do this.
The knuckleduster, the first dail
The very first rotary dials did not have a round fingerwheel. The very first ones were flanges with small scoops for the fingers, somewhat like a water wheel.
Later they deceloped into a kind of bracket with fingerholes attached to the outside. This gave it the appearance of a knuckleduster, giving rise to it’s nickname in Germany: Schlagring. See picture of a German version copy of this dial.
Please note that the distance between the first and last digit is much smaller than on the later models.
Turn the whole dial
On this US design the whole mechanism turns instead of just the finger wheel. It was made by BTMC in the 1910s and 1920s.
The reason why the whole mechanism dials? Probably to prevent friction from the fingertips rubbing off the numbers. This was a huge problem, with many solutions. Please mind that a dial is turned hundreds of thousends of times in its life. Dialing 10 telephone numbers a day can add up to 365.000 turns in one year alone.
No holes at all
This Danish dial does not seem to have any open finger holes at all. Again, it is a solution to the problem of the fading numbers. You can push the numbers inwards and when you retract your finger the number springs back. The numbers turn with the wheel, preventing finger rubbing.
Also it prevents dirt getting inside the mechanism.
You do not actually need holes to put your finger in. A dimple is enough to turn the wheel. And not having holes makes a cleaner design. Again this prevents dirt getting into the mechanism and the fingerwheel is easier to clean.
Not only was it used in the UK, but also on this Protea telephone from South Africa.
And there is a very rare model by the German company SABA that was produced for a short time just after WW2, that was equipped with a dimple dial.
Another finger wheel without holes: the daisy wheel. Besides a British prototype that never made it to full production, the only other example I know using this type of wheel is this Polish Bratek telephone by TELKOM. The advantage of this design is that the rim of the wheel omitted. The rim of regular fingerwheels often breaks off. Another reason for this design may be that it is easier to produce and uses less material than a regular dial.
Let’s go radical, no fingerwheel at all!
Saving the best for last: 2 types of dial that have no finger wheel at all.
First up is the so called keysender from the USA. It is a dialling unit especially for switch board operators. Not only does it have push buttons, but it remembers the sequence of numbers that are punched in too. So the numbers can be punched in the numbers in quick succession and and the operator can go and do something else while the keysender goes on sending the chosen numbers over the telephone line.
Here is a video (not mine) on youtube showing how it operates.
In Germany, in the late 1930s, Siemens & Halske developed this: the Senkrechtwähler , Radzug Nummerwähler or the drum dail, the Trommelwähler. It was also an aid for switch board operator. Numbers are dialled by pressing a section of a drum down. It enabled the operator to dial slightly faster than with a normal dial and it was more ergonomic, putting less strain on the arms and shoulders of the operator, making their life easier. Please keep in mind that switch boards could be very very busy indeed and the life of an operator could be very busy and stressfull.
A version of this trommelwähler was also built into an actual telephone, the Siemens & Halske Fg tst 261. See this article. It didn’t catch on, unfortunately. The general public found it a little awkward to use and people tended to misdial when operating it.
Unfortunately I do not have such a Phone myself, yet…. at the time of writing this article that is. 🙂
Great article, Arwin.
The Bell System also tried a variant of the “Daisy Wheel” dial when looking for a new dial during development of the Trimline. A model can be seen here…
Thanks Paul, very interesting. I see there is a sort of drum dial on your page too. Didn’t know anyone else but Siemens made such a dial.
These pages are really informative, thank you for putting them together. Please could I, as a UK citizen, make a small correction: the British Post Office never used dimple dials. They were only ever used on PAXs in the UK.
Hi Mike, thank you for your feedback. I have adapted the text a little and removed the reference to GPO.