Analog multimeters use positive (red) and negative (black) test leads to measure current, voltage, resistance, and frequency. Also called analog multitesters, they receive electrical signals through their test leads that cause the indicator needle to move back and forth across a scale marked with units of measure. These analog units measure oscillating pulses, such as unstable voltages across faulty components. Unlike some digital multimeters, analog multimeters will not freeze up in severe hot or cold environments.