The essential elements of the development in-core reactor instrumentation system are. shown in Figure І-2. Dry tubes are provided in the reactor core, and the detectors are positioned vertically within the tubes by the mechanical drive hardware. At startup of the power plant, the counting and Campbell detectors are located at an initial in-core position and are connected to their respective electronics assemblies by means of specially shielded cables. The counting electronics provides a seven-decade log count-rate meter indication, an analog recorder output voltage for the log count rate (level), and a meter indication and analog recorder output voltage for the reactor period. The Campbell electronics provides a recorder and meter indica­tion output in linear switched increments over six decades. Auxiliary functions such as trip. signals are also provided by the Campbell system. As the reactor is brought to full-power conditions, the in-core detectors are retracted. from the high-flux region and ultimately stored several feet below the core bottom.