Abstract: It is the object of the invention to suppress electromagnetic radiation caused by the ground potential of a printed-circuit board, which now becomes an important problem, as the bit-rate of digital signals increases. The ground-pattern of an electronic circuit mounted on the printed-circuit board is connected to the shield-case of an electronic circuit apparatus via a conductor-piece, noise generated by the electronic circuit is by-passed, and electromagnetic radiation of noise from a cable connected to the printed-circuit board via a connector can be suppressed.

Abstract: In an active plug-in circuit, a mode setting section sets either a plug-in mode or a regular mode, depending on the power source voltage of a package. When the plug-in mode is set, a power consumption controller maintains an electronic circuit built in the package in a low power consumption mode. After the power source voltage of the electronic circuit has been stabilized, the mode setting section sets the regular mode. The circuit reduces the variation of power source current to occur when a power source pin mounted on a package connector is connected to the corresponding terminal of a mother board connector and on the transition from the plug-in mode to the regular mode.