Abstract: An optical data storage system is contemplated, one employing a data-modulated writing laser beam (FIG. 2: .circle.L ) with improved associated optical media (FIG. 2), these characterized by multiple layers (FIG. 2:c,d,e,f,g)--more particularly, a highly reflective aluminum layer (c), a relatively transparent polymer spacer layer (d) overlying the reflective layer, and an optical absorber (recording) layer (e) overlying the spacer layer, plus an overcoating structure, e.g., as a "soft pad" layer (f; e.g., a fluoropolymer) on the absorber, with a "Hard" layer (g; e.g., a radiation-cured acrylic) laid over the "soft pad" as an outer protective overcoat. "Spiral" coating techniques (FIG. 3) are specified for applying the "Hard" layer.

Abstract: A pin-shaped handheld test probe particularly adapted to current mode logic levels indicates through a plurality of visual indicators HIGH, LOW, MIDRANGE, OPEN and SUPPLY VOLTAGE logic levels. Each visual indicator is controlled by the output of at least one comparator amplifier having one of two inputs resistively connected to a testing point and the other input resistively coupled to a stable reference voltage level generated by a zener stabilized precision resistor ladder network. The testing point is voltage biased to give an indication of OPEN when the test probe is attached to a pin or point which is unconnected.

Abstract: An Input-Output Interface Data-Transfer Control Unit, designated as a Line Control Processor, which provides the execution of instructions in accomplish data transfers between a main data processing system and a plurality of different types of peripheral devices. Further, said Line Control Processor provides for the buffering of at least two complete blocks of message data, thus to prevent access errors, since complete record length message transfers can occur in any given data-transfer cycle. The Line Control Processor operates with a standard communications and control discipline which makes the eccentricites of various types of peripheral units transparent to the main system. The Line Control Processor executes data-transfer instructions within the overall system thus relieving the central processor of an involvement in these tasks.