Abstract: A densitometer apparatus (200) is disclosed and is adapted to provide color density measurements of opaque materials. The densitometer apparatus (200) comprises a light source unit (202) having a source light (204) projecting light through a collimating lens (206). Light rays transmitted through the collimating lens (206) project through an aperture (208). The rays are projected onto an irradiated area surface of an object sample (212) under test. Electromagnetic radiation in the form of reflected light rays (214) are reflected from the sample (212). The reflected light rays are directed through a spectral filter apparatus (216) and impinge on receptor surfaces of photo-voltaic sensor cells (232, 234, 236). The sensors (232, 234, 236) generate electrical currents having magnitudes proportional to the intensities of the sensed light rays.

Abstract: A master computer of a controlled system is interrelated with the executory computer of a peripheral device via a standard serial interface. This relationship centers in the programming of the executory computer to make available on command from the master computer substantially all of the functions of the peripheral device, as well as the data stored in the executory computer, and also to lock out the keyboard of the peripheral device on command to prevent operator intrusion.