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Theory of Operation
3–20
1780R-Series Service Manual
U1105 is a logic array that selects the timing rate (pin 16) for the logic on this
schematic. HSYNC or VSYNC is selected depending on whether the horizontal
sweep rate is at a line rate or field rate.
Voltage Cursors. U1019B is the Voltage Cursor Amplifier. Upper and lower
voltage levels are determined by the Microprocessor, and are stored by the
Sample-and-Hold circuits on Diagram 12. The Cursor Select control line from
the Readout Engine (Diagram 21) is converted to a bipolar signal in U1105.
Line Strobe Out. In line select operation, a TTL high pulse appears at the Line
Strobe Out rear-panel BNC connector during the selected line time. Jumper
J1103 can be moved to its other position to send the Field 1 pulse from the SCH
circuit instead of the line bright-up pulse.