# What is the first (say early) use of switches (mechanical or electromechanical) for sake of processing (like automatic motor control)simple data?

Switches are intended for just turning ON or OFF the power supply by either closing or opening the circuit.

I often wonder how does mankind got idea to use these switch for sake of processing (simple processing like motor control) even before the thought of using Boolean algebra for analysing switch networks in mid 1930s.

What are some early applications which used switches not just mere purpose of turning ON or OFF the circuit but for processing?How may be these early devices be developed without aid of Boolean algebra?

Switches are intended for just turning ON or OFF the power supply by either closing or opening the circuit.

Not really. Switches in process control are intended to sense a state. That the result and its use can be combined is rather a nice shortcut.

Already early on, contactors were used to control power machienery with lower voltage circuits, itself controlled by series of switches, either direct handeled, or by prior contactors - like having Motor B only running if A is already running and up. Same is true for mechanical constructions.

I often wonder how does mankind got idea to use these switch for sake of processing (simple processing like motor control) even before the thought of using Boolean algebra for analysing switch networks in mid 1930s.

Relais are around since the 1820s and have been used for logic combinations since short thereafter - way before Boole wrote his book in the 1840s. Practical use of logic has been around since maybe the begin of time - and documented since Roman times.

Each Cuckoo clock is a piece of staggered logic for process control. More so every tower clock ringing bells accordingly at the hour for the hour.

Bools book is an exercise to formalize logic notation and fix its notation as well as rules. History goes way before - as well as it's important to keep in mind, that in the way we understand it today, it was developed in the 1900s to 1930s. And it wasn't until after Shannon that it became a valid tool for engineering.

What are some early applications which used switches not just mere purpose of turning ON or OFF the circuit but for processing?

Turning on and off is an inseparable result of processing. Even no matter how trivial it may seam. And all of this processing has been used way before any electricity.

Think of a lever moved by water level, pressing a plug into a tube when the level gets to low, thus saving a mill from getting overflown and damaged when stuck because of not generating enough power to drive whatever machinery. Clearly some (analogue) processing of water level vs. power requirement.

How may be these early devices be developed without aid of Boolean algebra?

Take above lever and plug and replace it by a switch and solenoid. Or as control circuit for the generator, switching of users when power level slides, or many alike.

• Logic is independent of implementation,
• Implementation can be done in many different ways, analogue and digital, electrical and mechanic, and finally
• Boolean Algebra is only a way to express logic in as a formal system, not precondition nor result of processing.

Bottom line: It's not applicable to condition on independant areas.

• Possibly just a translation issues, but switches dont' "sense" state, they set it.
– cjs
Nov 26, 2019 at 22:51
• @CurtJ.Sampson Switches are sensors detecting a condition. Think the switch in your microwaves door. It senses the door state so the microprocessors can run the microwave tube or not. Likewise the track zero switch on a classic floppy drive, or any other switch - like in Chenmunkas great example. Keep in mind, this is about process control. Nov 26, 2019 at 22:58
• Ah, now that you've edited it to say "switches in process control" it's more clear (and it helps make the original question more clear, too).
– cjs
Nov 27, 2019 at 3:36

The first recorded use of relays in process control computing is in a patent granted to John Saxby in 1856. A brief description is given here.

They were used to control railway signalling. The 'interlocking' superseded the mechanical interlocking systems used in Victorian signal boxes. It was only permitted to set a signal to "Proceed" if the track behind it was clear and points correctly set etc.

It is interesting to note that relay interlockings are not only still in use on the world's railway systems, they are still being manufactured in almost the same format as well over 100 years ago. Modern SSI (Solid State Interlockings) still use the same relay logic as these safety-critical relay systems.

(I spent a significant part of my working life programming these things).

• Well, they are as well still used in many other industrial applications. In fact, next to any modern SPS programming languages still supports constructs the were once used to describe alike relay based logic. Nov 26, 2019 at 18:42
• Indeed so. Ladder logic and similar constructs are widespread. Nov 26, 2019 at 18:48

Maybe not the earliest, but early and important, and very elaborate uses:

• Automatic telephone exchanges. Strowger, 1891.
• Elevator control (early 20th century).
• Telegraphy, especially teleprinters (from the early 1900s).