Abstract: There is provided a technology for realizing an PCI expansion adapter for a PC card which is connectable to a desktop type personal computer PCI expansion connector using a low profile PCI. The PCI expansion adapter includes an expansion unit which is provided with an electrical connector to a PCI bus, a low profile PCI expansion board provided with a PC card control element and an electrical connector to the PC card, wherein the low profile PCI expansion board and the expansion unit are connected by the electrical connectors mounted on the respective boards.

Abstract: In a level detector (17), a bias voltage is developed by a bias current to have a substantially constant difference irrespective of a temperature variation from a detected voltage produced by detecting a device output signal for use in TDM modulation. A control signal generator (19) calculates a substantially temperature independent difference digital value by subtracting a second digital value of the bias voltage from a first digital value of the detected voltage to produce an attenuation control analog level used in controlling a variable attenuator (11) which deals with a device input signal to produce an attenuator output signal with a desired value for use as the device output signal. Preferably, the detected and the bias voltages are amplified by a variable gain amplifier (35) controlled by a processor output signal.