Abstract: An optical-signal/electric-signal converting device communications system for a communications system that establishes communications using electric and optical signals. The converting device converts an electric transmission signal into an optical transmission signal and an optical transmission signal into an electric transmission signal. The converting device includes an electric signal receiving circuit for receiving the electric transmission signal transmitted from the host computer of the communications system through an electric transmission line, and a modulating circuit for modulating the electric signal sent from the electric signal receiving circuit into a pulse signal having pulses of a smaller width.

Abstract: An optical communications device is disclosed which is equipped with a transmission unit adapted to send binary-coded electrical pulse signals to another optical communications device in the form of optical pulse signals. The transmission unit includes a modulator for producing an electrical pulse signal of a narrow pulse width only at each of rising and falling edges in the binary-coded electrical pulse signals and an electro-optic converter for converting the electrical pulse signal of a narrow pulse width into an optical pulse signal of a narrow pulse signal. As an alternative, the transmission unit includes a modulator which produces an electrical pulse signal of a narrow pulse width for each bit in the binary-coded electrical pulse signals only when it is at a high level and an electro-optic converter which converts the electrical pulse signal of a narrow pulse width into an optical pulse signal of a narrow pulse width.

Abstract: A large scale integrated circuit has a first circuit section with input terminals external of the integrated circuit connected to output terminals of a second portion of the integrated circuit for use in an environment not requiring intrinsic safety. When the circuit is to be installed in an environment requiring intrinsic safety the external connectors are disconnected from one another. An excess voltage suppression circuit is connected to the external connections of the second circuit section.

Abstract: An optical communications device is disclosed which is equipped with a transmission unit adapted to send binary-coded electrical pulse signals to another optical communications device in the form of optical pulse signals. The transmission unit includes a modulator for producing an electrical pulse signal of a narrow pulse width only at each of rising and falling edges in the binary-coded electrical pulse signals and an electro-optic converter for converting the electrical pulse signal of a narrow pulse width into an optical pulse signal of a narrow pulse signal. As an alternative, the transmission unit includes a modulator which produces an electrical pulse signal of a narrow pulse width for each bit in the binary-coded electrical pulse signals only when it is at a high level and an electro-optic converter which converts the electrical pulse signal of a narrow pulse width into an optical pulse signal of a narrow pulse width.