Abstract: An electronic message transmission system including at least one transmission apparatus of the electronic message and a plurality of message receivers of the same wherein the electronic message is transmitted according to a predetermined transmission path connecting message receivers. A transmission state of the electronic message is memorized and up-dated in a memory and thereby, an addresser of the electronic message is able to know the state of the message transmission by referring to the contents of the memory.

Abstract: A device for detecting switch closure such as in a keypad for entering data comprising a matrix of conductor pairs and switches, each pair of conductors shorted by the pressing of a particular switch, and current-regulating devices on each conductor for limiting current in one direction and passing it without limit in the other direction. The device is driven by alternating current. The ends of the conductors in a conductor pair limit current of opposing polarities with respect to each other so that the signal on a shorted pair is an alternating current signal with a unique combination of a positive and a negative peak, which, when analyzed, allows the determination of which key was pressed. The binary identification of the pressed key is passed to the input port of a host device.

Abstract: Disclosed is a method and apparatus for highly stably and accurately generating a PAL video signal by digital processing. The method and apparatus comprise generating a basic clock having a frequency which is 11.times.N times (N: an integer) as high as a horizontal synchronization frequency F.sub.H, producing digital data of orthogonal color subcarriers, color difference signals and a luminance signal respectively with the timing of the basic clock, multiplying the digital data D.sub.B-Y D.sub.R-Y of the color difference signals by the digital data Dsin and Dcos of the color subcarriers respectively to obtain digital data of two kinds of modulation signals, adding the digital data D.sub.Y+S of the luminance signal to the digital data of the two modulation signals, and effecting digital/analog conversion of the addition to provide the PAL video signal.

Abstract: In a ring LAN system having a configuration control unit serially connected to a dual ring transmission line, the configuration control unit is provided with a transmission line reconfiguration control mechanism to disconnect a fault point upon detection of a transmission fault, such as a breaking of one of a twisted pair of cables, and after recovery of the fault, reconnect the disconnected point to restore the transmission line to its original state. The reconfiguration control mechanism suspends reconfiguration control if a reconfiguration operation counter counts more than a predetermined number of reconfiguration operations within a predetermined time period measured by a reconfiguration operation monitor timer, such as when a temporary fault occurs intermittently.