For full solid-state key telephone systems, high breakover voltage IC switches, which can connect to the central office lines directly and form a large scale matrix within a small volume, has been desired. Firstly, this paper compares several kinds of IC switches, which are suitable for formation of speech path matrix and shows that the photo-coupled PNPN crosspoint switch, connected in bridge format, is superier to the others because of low transmission loss, small matrix volume, reliability against lightning, self-latching speech path during power suspension and NTT technical requirements satisfaction. Secondly, the paper clarifies required electrical conditions for the PNPN element and the crosspoint circuit. They are breakover voltage above 300 V, dv/dt firing torelance above 160 V/0.1 µs, on-resistance within 9 Ω, less than 0.97 V forward voltage drop and restricting the reverse leak current which flows in the optically triggered PNPN element. Next, the IC switch structure is described, along with available technologies to satisfy the electrical requirements, such as canal isolation, highly efficient photo coupling structure and light shielding of anode junction. Actual IC switch characteristics satisfy all required values.

In a display system with a line-of-gaze (LOG) controller, it is difficult to make the directions and motions of a LOG-controlled object coincide as closely as possible in the display with the user's intended LOG-directions and motions. This is because LOG behavior is not only smooth, but also saccadic due to the problem of involuntary eye movement. This article introduces a flexible on-line LOG-control scheme to realize nearly perfect LOG operation. Using a mesh-wise cursor pattern, the first visual experiment elucidates subjectively that a Kalman Filter (KF) for smoothing and predicting is effective in filtering out macro-saccadic changes of the LOG and in predicting sudden changes of the saccade while movement is in progress. It must be assumed that the LOG trajectory can be described by a linear position-velocity-acceleration approximation of Sklansky Model (SM). Furthermore, the second experiment uses a four-point pattern and simulations to scrutinize the two physical properties of velocity and direction-changes of the LOG in order to quantitatively and efficiently resolve "moving" and "gazing". In order to greatly reduce the number of LOG-small-position changes while gazing, the proposed Gaze-Holding algorithm (GH) with a gaze-potential function is combined with the KF. This algorithm allows the occurrence frequency of the micro-saccade to be reduced from approximately 25 Hz to 1 or 2 Hz. This great reduction in the frequency of the LOG-controlled object moves is necessary to achieve the user's desired LOG-response while gazing. Almost perfect LOG control is accomplished by the on-line SM+KF+GH scheme while either gazing or moving. A menu-selection task was conducted to verify the effectiveness of the proposed on-line LOG-control method.