The AT 2500 consists of two main assemblies. The Main Tuner Assembly houses the high power RF components in the RF compartment on the right side and the two printed circuit boards in the compartment on the left side. These PC boards control the motor-driven high voltage capacitors in the RF compartment. The tuner portion has been designed so that it can be operated automatically after the band switch has been set, or manually by operating the tune and load capacitor knobs after the automatic feature is switched off. This manual feature makes it possible to operate the tuner in case of failure of the electronic portion of the unit. Should you have to return the plug-in PC Control Board to the factory for repair, you will still have a manual antenna tuner. However, an external SWR and power meter is needed. The second assembly consists of a Remote Directional Bridge Coupler which connects to the main tuner assembly via a captive plug-in cable.