Abstract: This portable ultrasonic detector has a moved distance instrument comprised of an encoder for detecting a moved amount and a counter for counting the moved amount signal outputted from the encoder, as a means for obtaining position information of an ultrasonic probe. When moving the ultrasonic probe on the surface of the object on the occasion of the inspection, the moved distance instrument measures the moved amount of the ultrasonic probe. The measured moved amount of the ultrasonic probe is sent to an arithmetic processing section of the device body. Also, the ultrasonic detector detects A-scope data when scanning the inspected object with the ultrasonic probe, and executes the predetermined processing by using the data. The ultrasonic detector combines the A-scope data and the moved distance data of the ultrasonic probe to make an inner scope image (B-scope image, etc). When repeatedly scanning the same spot of the object with the ultrasonic probe in order to make the B-scope image, etc.

Abstract: A gain of a variable gain amplifier circuit is controlled by applying a signal of a predetermined voltage level to the variable gain amplifier circuit during an idle period of an ultrasonic receiving signal, deriving an output from the variable gain amplifier circuit, comparing it with a voltage level obtained as an aimed value by a gain regulator or other control circuit of an ultrasonic signal amplifier circuit including the variable gain amplifier circuit and producing a gain control signal according to a difference resulting from the comparison to control the gain to the aimed value until the difference becomes zero. The gain of the variable gain amplifier circuit set in the idle period is maintained during a measurement period of a subsequent receiving signal so that the latter is amplified with the maintained gain. Thus, a stepwise and selective gain setting corresponding to the aimed value can be obtained by controlling the gain of the variable gain amplifier according to the aimed value.

Abstract: An ac type line concentrator for use in a data communication system, comprising a crosspoint switch circuit. The crosspoint switch circuit is constituted by a plurality of crosspoint switches capable of switching an analog signal (hereinafter referred to as an analog switch), so that a carrier signal modulated by a data signal may be transferred from one of m incoming lines connected with m terminal units to a selected one of n(n<m) outgoing lines connected with a central unit through the ac type line concentrator without being demodulated.