Figure 6. Oven-controlled crystal oscillator.

Figure 6.

Oven-controlled crystal oscillator.

Digit Driver Transistors Q10-Q20.

The minus sign is driven by Q9.

The

annunciators are fixed symbols which are backlighted by incandescent lamps.

Cathode driver transistors Q1-Q8 are used to enable the segments for the

decimals, minus sign and decimal points.

The result of a measurement is displayed by using a strobing

technique. That is, only one digit of the displayed number is on at any one

time.

One digit is displayed and then removed; then the next digit is

displayed and removed. This process is continued until all digits have been

shown.

The strobing process occurs at a faster rate then the eye can

detect, so the display appears continuously lit. The 4 line to 7 Segment

Decoder, U6, controls the digit (numeric character) to be displayed, while

the BCD-to-12 Line Decoder (U1) controls the placement of the digit in the

display.

The

BCD

data

lines

carry

the

digit

information

from

the

Adder/Subtracter to the character generator (U6). The BCD lines are decoded

by U6 into segment lines for the LEDs.

Each segment line enables an

individual segment of the LED display.

Each of these segment lines are

connected to the same segment in each digit. The turn-on of these