DEC DECtape 551 Manual page 79

EXAMPLE
Figure Al-2 illustrates Digital symbols and nomenclature. The circuit shown is a Type 4303
Integrating Single Shot used to control the enabling time of several gates. The module is located
in the twelfth position from the left (when viewed from the front or wiring side) of mounting
panel B (the second from the top) in cabinet 1. The symbol marked DELAY is a monostable
multivibrator with two complementary outputs, terminals U and W. In the 0 state, these terminals
are at - 3 v and ground as shown by the diamonds inside the symbol on the left. The
~
3 v from
terminal U is the assertive level for a gate in 2018 and is applied to terminal F as the SAFE sig-
nal. When the multivibrator is triggered, it momentarily goes to the 1 state and terminals U and
W reverse their voltage levels, as shown by the diamonds representing the 1 state conditions.
Term i na I U now prov i des a ground assert ive I eve I to term i na I M of a gate in 1 B 15, and term ina I
W provides a - 3 v pssertive level to terminal F of a gate in 1002. The time the multivibrator
remains in the 1 state is a function of the capacitor selected by jumpering terminal 0 to terminal
E and the setting of the external potentiometer between terminals X and Z.
The multivibrator is triggered to the 1 state when anyone of three signals occurs. One of these
is a positive pulse designated GO from a pulse amplifier in 1C12. Another is a negative pulse
designated SAMPLE from a NOR gate in 1 C21, which is appl ied to the base of an inverter.
The third is the positive transition at the trailing edge of the START signal, a negative level
from a delay in 1B11. This will only trigger the capacitor-diode gate when a ground signal
designated OPEN from a fl ip-flop in 1 B13 has been present for at least 1 tJsec.
SAFE
TO 1B15M
TO 2D18F
TO 1 D02F
: 4303-
- -
-
----
- -
-
I u
w u
W
1B12
DELAY
I
GO
I
1C12H
VARIABLE
START
I
1 B 11 J
D
I
SAMPLE
1C21Z
L
X
Z
T
- -
- -
-
R5 10Kn
OPEN
TIME
1B13H
Figure A 1-2
Typical Digital Logic Block Diagram
Al-6