The Casing Collar Locator is designed to detect the presence of collars in the well bore casing or tubing. The instrument consists of a wire coil, two magnets, and associated circuitry. The magnets are positioned with like poles facing each other and the coil is placed between them. This configuration produces two adjacent magnetic flux fields passing through the coil. Any change in the metal density per unit volume passing by the tool will alter the flux field and produce a signal from the coil. This signal is then processed by the CCL internal circuitry and sent up the cable to the surface. At the surface, the signal is processed by the CCL circuit in the Line Power Module and the output is sent to the recording device.