Multiple input crosspoint group with common output amplifier and independently variable switching circuits

Abstract

Abstract A MULTIPLE UNIT CROSSPOINT GROUP WITH COMMON OUTPUT AMPLIFIER IS DISCLOSED WHERE AT EACH CROSSPOINT OF THE GROUP IS DISPOSED A VIDEO SWITCHING CIRCUIT HAVING AN INDEPENDENTLY VARIABLE TRANSFER FUNCTION. EACH SWITCHING CIRCUIT IS CONTROLLED BY ITS OWN CONTROL SIGNAL TO PERMIT OR PREVENT THE PASSAGE OF A VIDEO SIGNAL APPLIED THERETO. EACH SWITCHING CIRCUIT INCLUDES MEANS TO PROVIDE DELAY LINE EQUALIZATION AND TO COMPENSATE FOR ATTENDANT ATTENUATION WHENEVER THE VIDEO SIGNAL APPLIED THERETO IS THE OUTPUT FROM A DELAY LINE. EACH OF THE SWITCHING CIRCUITS IS CONNECTED TO A COMMON OUTPUT STAGE WHICH PROVIDES AN OUTPUT SIGNAL CORRESPONDING TO THE ACTIVATED SWITCHING CIRCUIT. THE OUTPUT FROM THE OUTPUT STAGE IS ALSO CONNECTED BACK TO ALL OF THE SWITCHING CIRCUITS AS A NEGATIVE FEEDBACK SIGNAL. IT IS ON THIS SIGNAL THAT THE GAIN ADJUSTING AND EQUALIZING CIRCUITRY OPERATES. THE SWITCHING CIRCUITRY INCLUDES A DIFFERENTIAL AMPLIFIER, ONE INPUT OF WHICH IS CONNECTED TO ITS ASSOCIATED VIDEO SIGNAL AND THE OTHER OF WHICH IS CONNECTED TO THE AMPLITUDE ADJUSTED AND EQUALIZED NEGATIVE FEEDBACK SIGNAL. THE DIFFERENTIAL AMPLIFIER INCLUDES A CONSTANT CURRENT TRANSISTOR WHICH FEEDS BOTH TRANSISTORS OF THE DIFFERENTIAL AMPLIFIER. THE CONSTANT CURRENT TRANSISTOR IS RESPONSIVE TO THE CONTROL SIGNAL TO THEREBY SWITCH THE SWITCHING CIRCUIT ON WHENEVER THE CONTROL SIGNAL IS PRESENT. ALSO DISCLOSED IS CIRCUITRY FOR INSURING THAT WHENEVER ONE OF THE SWITCHING CIRCUITS IS ON THE OTHERS ARE TURNED OFF.

Inventors

• 👤 Ole Skrydstrup

Bibliographic Details