Abstract: In order to propose a signal input and output apparatus for changing over control depending on a detection result by discriminating the type of signals when signals of two or more types are passed in the same signal line, a signal input and output apparatus comprises signal discrimination changeover means for discriminating the type of control signal through cable, plug and jack, as a transmission path generating a discrimination signal, supplying it to a controller, and changing over the control of a signal processor to the controller on the basis of the discrimination signal, and thereby input and output of plural control signals can be processed through a single transmission path. As a result, by a single jack only, plural signals can be passed on the same transmission path by optimizing the transmission and reception paths and transmission and reception elements, and therefore the parts mounting area can be saved, and states of various types of signals can be detected.

Abstract: A video signal AGC circuit including an analog gain control amplifier for adjusting the level of an input analog video signal; an A-D converter for converting the output of the analog gain control amplifier to a digital video signal; a sync level detector for detecting the sync level of the digital video signal outputted from the A-D converter; a digital gain control amplifier for adjusting the level of the digital video signal outputted from the A-D converter; a first control signal generator for generating a first control signal to adjust the gain of the analog gain control amplifier on the basis of the output of the sync level detector; and a second control signal generator for generating a second control signal to adjust the gain of the digital gain control amplifier on the basis of the output of the sync level detector.

Abstract: A video tape recorder has a recording current setting unit for setting recording currents to be supplied to a recording head for recording audio and video signals on a magnetic tape. The recording current setting unit controls electronic volume controls to adjust and output audio and video signals to set the recording currents. Level detectors detect reproduced signals, which have been recorded on the magnetic tape by the recording head, and supply the detected signals to the recording current setting unit. The recording current setting unit controls the electronic volume controls to hold the audio signal at a constant level and to simultaneously vary levels of luminance and chrominance signals of the video signal with the levels being kept at a constant ratio, and at the same time controls the recording head to preliminarily magnetically record the audio and video signals on the magnetic tape.