Voltage Switch and Output Gate

TM 11-6660-204-25

V306. Test jacks J315 and J316 (fig. 27) are

the reverse direction, and thus rapidly restores

provided to check the grid waveforms of tubes

the circuit to its original stable state with tube

V305A and V305B, respectively. The cathode

V305A conducting and tube V305B at cutoff.

waveform is shown at jack 318 of tube V305B.

d. The grid of tube V305B is directly connected

through resistor R330 to the grid of voltage

A positive pulse from the cathode of pulse

switch tube V306; thus, the positive rectangular

selector tube V304A is impressed on the cathode

pulse created at this point (J316) is used to oper-

of tube V305A through capacitor C306, to reduce

ate V306.

the nearly zero bias to a high negative value

which reduces plate current and produces a posi-

2-11.

Voltage Switch and Output Gate

tive plate voltage swing because of the reduced

(fig. 2-8)

voltage drop across resistor R323. This plate volt-

age swing is coupled to the grid of tube V305B

a. Voltage switch V306 is a miniature, hi-rep,

through C308 producing a plate current flow

twin-triode tube. Both sections are connected in

which increases voltage drop across R327. Capaci-

parallel, but they are shown as a single tube in the

tor C308 permits the instantaneous signal swings

simplified diagram of figure 28 for ease of pres-

to bypass resistor R324 so that this steep rise is

entation. The output gate circuit utilizes both sec-

not attenuated at the grid of tube V305B. This

tions of miniature twin-triode tube V307 con-

negaive plate voltage swing is, in turn, coupled to

nected as twin diodes. The rectangular pulse out-

the grid of tube V305A by capacitor C309, caus-

put from the univibrator is utilized to develop an

ing regenerative action which rapidly increases

output pulse (one that is identical for each input

the negative swing on tube V305A so the tube is

pulse) by voltage switch tube V306 for applica-

immediately driven into cutoff. This new state of

tion to the output gate circuit. The output gate

conduction exists until capacitor C309 is dis-

functions to produce a 0- to approximately 30-mil-

charged sufficiently through resistor R328 to the

livolt output voltage that is proportional to the

point where the grid of tube V305A is brought

recurrence frequency of the input signal applied

above cutoff. Regenerative action then occurs in

to the recorder.

Figure 27. Univibrator, simplified schematic diagram.

2-10