| 摘要 |
PURPOSE:To information immediately whether or not a signal is lost to the user by a video by providing a switching circuit of a synchronizing signal and a pseudo synchronizing signal and displaying a character or a graphic at no signal withthe pseudo synchronizing signal. CONSTITUTION:A phase dissidence detecting means 12 detects the dissidence of the phase between a horizontal synchronizing signal (a) and a flyback pulse C and drives a synchronism changeover control means 23. The synchronism changeover control means 23. The synchronism changeover control means 23 controls a switch drive means 24 so as to switch a switch circuit 28 to the positions A and A' and also controls a pseudo synchronizing signal generating circuit 25 so as to oscillate a horizontal oscillation circuit 26 and a vertical oscillation circuit 27 and its output signal is given to horizontal and vertical deflection coil drive circuits 16, 19 via the switch circuit 28. A character generator 20 reads the character pattern stored in advance from a character pattern storage device 22 at the same time, generates a character signal and informs the no signal by displaying it on a cathode ray tube 5.
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