The Dummy Load.

This is only ever needed for testing a radio. It is used to provide the CB with what appears to be a perfect antenna, so that the person can take accurate measurements such as power.

In its simplest form, the dummy load is nothing more than a resistor that matches the output impedance of the radio (50 Ohms for CB). The power put into the load is dissipated as heat rather than radio waves, which is why the load usually has fins to help to get rid of that heat.

There are different types of dummy load, rated at different power levels and with different features. Some dummy loads use a bulb, so they light up to show that there is output from the radio.
Please note that the bulb is a special type, you cannot use just any bulb for this purpose.

There are also other loads for higher power levels and some may even include a power meter. For legal CB a basic 10 Watt load is good enough, and loads such as the one shown on the right are unnecessary.