Test Light and DVOM
NOTE: Most circuits include solid-state devices. Test the voltages in these circuits only with a 10-Mega ohm or higher impedance digital multimeter. Never use a test light or analog meter on circuits that contain solid-state devices. Damage to the devices may result.
On circuits without solid-state devices, use a test light to check for voltage. A test light is made up of a 12 Volt bulb with a pair of leads attached. After grounding one lead, touch the other lead to various points along the circuit where voltage should be present. The bulb will go on if there is voltage at the point being tested. If you need to know how much voltage is present, use a Digital Volt/Ohmmeter (DVOM).