An improved robotic thumb for a robotic hand assembly is provided. A video signal switching apparatus and circuitry, including an electronic crosspoint switch, enables switching very high speed video signals. The ECRV can also be used in connection with a conventional zoned HVAC system to provide additional control and additional zones not provided by the conventional zoned HVAC system. To increase the effectiveness and reliability of a manipulation or tuning protection of the data, a code word is stored in the data, which is checked while the microcomputer system is in operation, and the measures are activated or deactivated as a function of the result of the check of the code word stored in the data. A polarization rotation element may be used to orient the polarization of the light passing through it to control the amount of feedback light.