ITT - Index of

APPLICATION NOTES
FOUR-LAYtErFi2 DOODlE
Figure 15
Figure 16
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VI
T
Ring Counters
The basic requirement of a ring counter is
to turn one stag e at a time ON in a simple
progression. Each time a trigger pulse is applied,
the ON stage will advance one stage.
The circuit forms a closed loop, or ring, so that
when the final stage has been activated the
next pulse will move the ON condition back to
the first stage where the cycle begins over
again. In Figure 17, one stage will turn ON as
soon as power is applied. The commutating
capacitor C between the ON stage and the
next successive stage charges through RL and
the ON 4-layer diode to VA, which is less than
the Vs of the diodes and keeps them from turning
ON. A trigger pulse, either positive or
negative, causes VB to drop almost to ground
potential, which in turn, causes VA to drop at
the same time due to the coupling action of Cl.
Since Rl is large enough so that a current of
less than Ih flows through the trigger diodes, the
pulse is only momentary. The drop in voltage
at A turns OFF the ON diode. At the same
time Cl begins to charge and the voltage at A
rises again.
The voltage at the high end of the charged
commutating capacitor C adds to VA causing
the next stage to fire. The repetition rate of the
output pulses equals the rate of the trigger
pulses divided by the number of stages.
A different steering circuit is shown in Figure
16. Assume thot Dl is ON. Point A will be ap·
proximately at ground potential and paint B
at VI. When a negative pulse is applied it is
blocked by CRI but passes through CR2, causing
swilchaver to take place. Current from V2
passes through Rand D2 to ground. The principal
source of current for the conducting branch
is V2. The RL'S are need"ed to maintain a voltage
of less than V. across the OFF diode.
Figure 18
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Figure 17
Telephone Switching
When trigger signals of the polarity shown
in Figure 18 are simultaneously applied to the
lines, one of positive polarity to lines I, 2, or 3,
and the other of negative polarity to lines
4, 5, or 6, two of the lines will be connected.
If triggers are applied to lines 2 and 5 as
shown, the 4-layer diode A will conduct connecting
them together. The series resistors
allow a current greater than Ih to flow, thus
keeping the diode in the ON state. To open the
circuit, a contact is opened to interrupt the
flow of current through the diode which will
then revert to its 0 FF condition.
15-11