The lock-on circuit, consisting of oscillator (¥V-17), amplifier
(v-16), the push button switch (S- ), and relay (K-) is used only
with the telephone telemetering system.
When 4 remote ground
.
monitoring station is called, a timer holds the line for two minutes.
If telemetering for a longer period is required, the lock-on button is
pushed which places the 2,00 cps tone generated by the oscillator
(V-17) on the telephone line.
This line actuates a latching relay
at the monitoring station which will hold the line until the Receiving
Station release switch is pressed.
The 2400 cps tone, its third harmonic (7200 cps) and 60 cps which
is often picked up on telephone lines are attenuated by filters F-1,2
and 3 respeotively.
The filters prevent these signals from affecting
the Receiving Station circuits.
The filter circuits remain in the
circuit for all types of operation although they are only necessary
when using telephone lines and lock-on system.
The circuit from
this point on, is common to both aerial and ground telemetering.
Pulses from the radio receiver are amplified and shaped by V-l,
V=2 and their associated circuitry, actuating Sohmitt Trigger, V=3.
For each input pulse (Fig. 19a) this stage delivers a uniform sized
positive pulse, (Fig. 19b).
This is fed through a cathode follower
V-LB into a diode coupled (V-5B) step-charger, consisting of
capacitors C=-51 and C-52.
While one of these capacitors is being
charged by the pulses from the Schmitt trigger, the voltage of the
other, developed by the previous pulse train, is read by a VIVM bridge
(V-11 and V-12) whose output drives the strip chart recorder.
Either
three decade recorder chart paper san be used to read the intensity
-i -