Have you ever taken apart an electronic device that no longer works, like an old clock radio or VHS tape player, just to see what it looks like on the inside?

Inside most electronic devices, you'll find a circuit board (or circuit card; it's all the same), which is a flat, thin board that has electronic gizmos mounted on it.

In most cases, one side of the circuit board is populated with tiny devices that look like little buildings. These are the components that make up the electric circuit: the resistors, capacitors, diodes, transistors, and integrated circuits that do the work that the circuit is destined to do.

The other side is painted with little lines of silver or copper that look like streets. These are the conductors that connect all the components so that they can work together.

An electronic circuit board looks like a little city! For example, have a look at a typical circuit board. The top of the card is peopled with a variety of common electronic components. The underbelly of the circuit card has the typical silver streaks of conductors that connect the components topside so that they can perform useful work.

Here's the essence of what's going on with these two sides of the circuit card:

• The component side of the card — the side with the little buildings — holds a collection of electronic components whose sole purpose in life is to bend, turn, and twist electric current to get it to do interesting and useful things.

Some of those components restrict the flow of current, like speed bumps on a road. Others make the current stronger. Some work like One-Way street signs that allow current to flow in only one direction. Still others try to smooth out any ripples or variations in the current, resulting in smoother traffic flow.

• The circuit side of the card — the side with the roads — provides the conductive pathways for the electric current to flow from one component to the other in a certain order.

The whole trick of designing and building electronic circuits is to connect all the components together in just the right way so that the current that flows out of one component is passed on to the next component. The circuit side of the board is what lets the components work together in a coordinated way.

Do not under any circumstances plunge carelessly into the disassembly of old electronic circuits until you're certain you know what you're doing.

The little components on a circuit card can be dangerous, even when they are unplugged. In fact, the tall cylindrical components — called capacitors — can contain stored electrical energy that can deliver a powerful — even fatal — shock long after you've unplugged the power cord.