An asymmetric switch

The glow of Christmas was fading. The gifts were all opened, but this year it was somehow different from the previous ones. My 10 or 11 year old self had received a present which was not fully explored. In earlier years, the battery-operated toys would have been worn out in a few days or board games would have been played a few times already. In the immediately preceding year, the toys had their fully functional motor yanked out and the two cubical magnets within it brutally extracted. This particular year, however, I had received a gift which called for higher powers. The maroon box simply labeled "Electric Set" (or something equally prosaic) had wires, batteries and other gizmos that I had not been able to connect up in a satisfactory manner yet. I knew I needed help.

On asking my dad, he took a look at the instruction booklet that came with the box and declared that even higher powers would need to be invoked. Recently we had acquired a neighbor who was an engineer. My dad promised to ask him to help me out with my new toy. Comforted by this I decided to take a fresh look at the indecipherable instructions and try and fathom the mysteries therein.

One of the first things was a bulb wired up to a battery. Two wires wires was all that was required. The soft yellow light of the bulb was but a faint hint of the pride that glowed within me. I had connected up a bulb to a battery all by myself! I connected and disconnected the cables several times to prove that it wasn't just luck. It worked every time.

The electric set had a door bell with two terminals for attaching wires. With the newly earned confidence, I replaced the bulb holder with the bell. The bell rang. How wonderful that sounded! With my bare hands I had made a bulb light up and a bell ring. The road ahead, which once looked rocky and unfamiliar, appeared approachable.

A look at the instruction book revealed that they had a push-button in their bell setup. No problem, I said, and proceeded to add the button to mine.  I could see a definite need for the button: my bell kept ringing all the time whereas, in practice, a bell should only ring when someone pushed a button. I wired it up but the effect was the opposite to my expectation. It stopped ringing when the button was pressed and rang when the finger was taken off. This by itself was not alarming; what had me worried was that the batteries warmed up when the switch was pressed. I took a good look at the 4 wires and could see nothing amiss. Yes, I needed help. The neighbor's engineering skills were required to get me on the right track again.

Fortunately, I did not have to wait long. My dad had approached Mr. Purushottaman and a time had been agreed upon. On the appointed day I walked to the neighbor's apartment and rang the bell. Yes, that bell worked it should have; it did not ring when the button was left unpressed. I knew that mine was not a fundamental problem and that Babu's dad - which is how we referred to Mr. Purushottaman - would show me how to correct my mistake. There was a smile on his face when I showed him my bell circuit. Two deft changes and it worked as it should have. I was amazed. My inner aesthetic sense had called for symmetry and that was how my circuit was wired up. There was total disregard to how switches worked.

But a fresh look at the newly wired bell circuit showed that symmetry had no place in it. I could see what the switch was doing: it broke the flow of current to the bell. The reason for the battery getting warm would remain a mystery for many more years, but that is another story.

The electric set had one more apparatus that required attention. It was -what I later came to know - an induction coil. One can generate high voltage with it.  The ignition system of a car - at least in the older models - is based on this technique. Babu's dad explained how that was to be wired up. A few minutes later it was ready to be tested. On pressing the switch it began to buzz and a bluish spark danced near the contacts. This wasn't the most exciting part of it. There were two hollow metal cylinders attached to terminals on the induction coil mount. I was told to hold them one in each hand. I could feel a tingling sensation running through my arms when the switch was thrown.

A variant of this was mentioned in that once formidable instruction booklet. It required a cylinder to be placed in a bowl of water with me completing the circuit by dipping a finger in the bowl and holding the second cylinder in the other hand. The same tingling sensation again. Babu's father explained that electricity was flowing from the induction coil through the bowl of water and me back to the induction coil. That brought us to the end of the instruction booklet. All experiments had been performed and no mystery was left to be explained. I thanked Babu's dad and walked back home with a proud springiness in my stride. I showed what I had learnt to my dad.

Little did I know that a few years later, I would be studying electrical engineering and move on to software engineering where I would be controlling millions of tiny switches. Electronic gates so small that one cannot see them; their effects, however, are harnessed by millions every second. As I write this there are infinitesimal wires that carry current to form the letters that you are reading. The afternoon that Babu's dad showed me how to wire up a bell and an induction coil was an inflection point in my life. It was not what started me on my path towards where I am today - that was decided by my grandfather who had unilaterally declared that I was to be an electrical engineer. We all end up in places we least expect but once there, on looking back, it only seems logical that we took that path. At every point on the way there are angels that point out the direction to you. Mr. Purushottaman, thank you.