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5.27 Schematic of 4013 flip-flop

The output from the 4028 can be used directly to turn a switch or
circuit on or off. However, this isn’t an optimum situation, because
as soon as you key another number (channel), the previous channel
turns off (brings the line low).
The solution to this problem is a 4013 D-type flip-flop (see Fig. 5.27).
The flip-flop is a basic computer memory datum. In this circuit it is
configured as a divide-by-two counter. Upon receiving the first “on”
signal from the 4028, it turns its output line high. When the 4028
brings the line low, which happens when hitting another channel, the
4013 will keep its output line high (latched).
To bring the 4013 output line low, simply key the channel for a
second time. The second high signal to the 4013 brings the out-
put line low (unlatched). One can continue to bring the 4013 output
line high and low by alternately switching the input line high.

Machine vision

To reproduce human vision in a machine is a difficult task. One
cannot simply connect a video camera to a computer and expect it
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Chapter five