fork amplifier, and a dual output buffer. All
70. Scaled Fork Oscillator Unit
stages are supplied from the regulated +250-
The sealed fork oscillator unit, used in Fac-
volt source.
simile Sets AN/TXC-1 above serial number 105
on Order No. 2695-MPD-45 and in all Facsimile
diagram form, the signal paths in the sealed fork
Sets AN/TXC-1A, -1B, -1C, and -1D, is similar in
oscillator unit. One-half of V2 picks up the weak
purpose and performance to the unsealed unit
signal from the fork and amplifies it enough to
described in paragraph 69. However, the sta-
drive V1 so that the output of V1 is constant
bility of this tuning fork is improved by using
a temperature-compensated, bimetallic fork which
despite minor variations in input. The constant
is vacuum sealed to minimize the effects of atmos-
level output of V1 is amplified in the other half of
pheric and barometric changes. The frequency
V2, the output of which feeds the drive coils of the
must be maintained with extreme accuracy; a
tuning fork. Part of the output of V1 is impressed
slight variation will cause a change in motor
on V3, one section of which feeds the motor ampli-
speed and a loss of synchronization between
fier and exciter lamp amplifier circuit, and the
transmitting and receiving machines. A devia-
other section of which feeds the photocell bridge
tion in frequency of 1 cycle in 10 seconds will cause
modulator circuit. A complete schematic dia-
a skew of more than 1 inch in the received copy.
gram of the sealed fork oscillator unit is shown in
The sealed fork oscillator unit consists of three
stages: a fork input amplifier and driver, another
