[Cody]

Cody asked the Naked Scientists:
   
how does the game "Operation" work?

Cody

What do you think?

[Daerana]

Basically, the game works by creating a simple circuit.  The battery, light, buzzer, metal edges on the body and metal tweezers are connected by wires yet the wires do not go in a full circle.  ie. imagine that each part is like on a chain yet it wont work unless the chain is done up and goes in a full circle.  This is called a complete circuit.  To complete the circuit the metal of the tweezers must touch the metal edge of the body.  This connection works the same as a switch would in a simple circuit such as turning on a light.  When the circuit is complete the light and buzzer turn on from the power in the battery.  However, if the circuit is not complete this can't happen.

Hope this helps.

[RD]

To complete the circuit the metal of the tweezers must touch the metal edge of the body. 
 This connection works the same as a switch would in a simple circuit such as turning on a light.

It's a long time since I played operation, but isn't there a latch circuit involved:
 even though the metal-metal connection may only be made momentarily the buzzer and light stay on until reset.
 
I may be wrong, like I said it's been a long time.

[Geezer]

I think you are right. Here's a simpler version - 

[diagram=620_0]

[RD]

A couple of 555 timer circuits would do it : one to make a latch and  one to make a buzzer.

[Geezer]

My "drawing" is a latch

[RD]

My "drawing" is a latch

The block diagram symbol for a latch is a rectangle: here is the RS latch in the 555 timer IC (coloured) ...

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More (rectangular) latch symbols here ... http://en.wikipedia.org/wiki/Flip-flop_%28electronics%29#Implementation

[Bored chemist]

Geezer's diagram, while spectacularly unclear, is a latch.
Perhaps more importantly, I think that game might have been going longer than the 555.
If so, I wonder what the original electronics were.

[RD]

I wonder what the original electronics were.

Could be made with a pair of transistors ... http://en.wikipedia.org/wiki/File:Flipflop_by_trexer.png

[Geezer]

Pretty much anything with more than unity gain could be used. That might be a couple of transistors, a relay, or a non-inverting logic buffer.

However, I have a vague recollection that the buzzer sounded for a bit, then shut itself off. If that's true, then a latch won't quite hack it. We'll need a monostable of some sort. That could be done with some sort of resistor/capacitor network to produce a time constant, combined with a couple of transistors, a relay, or a non-inverting logic buffer.

As relays tend to be a lot more expensive than transistors, I'd think it's most likely they used a couple of cheap transistors.

[Geezer]

With lots more detail.

 [ Invalid Attachment ]