A Turns on traveling-wave tube filament voltage
B Turns on traveling-wave tube helix and collector voltages;
energizes all transistor circuits associated with
communications experiments
AA Turns off traveling-wave tube helix, collector, and filament
voltages; de-energizes transistor circuits
C Turns on traveling-wave tube by applying anode voltage
CC Turns off traveling-wave tube anode voltage
D Turns on telemetry and energizes radiation experiment circuits
DD Turns off telemetry and de-energizes radiation experiment
circuits
E Turns on current in orientation torque coil
EE Turns off current in orientation torque coil
F Connects telemetry encoder No. 1 to circuit
FF Connects telemetry encoder No. 2 to circuit
SS Performs duties of AA, CC, DD, EE, and FF; de-energizes
136-mc beacon transmitter and removes all load from storage
battery
S Connects storage battery back into the circuit and energizes
the 136-mc beacon transmitter
T1 Turns off command receiver and decoder No. 2 for 15 seconds,
so that command receiver and decoder No. 1 can be tested
T2 Turns off command receiver and decoder No. 1 so that No. 2
can be tested
[Illustration: _This block diagram of Telstar I’s command circuit
shows the redundant receiver and decoder chains, No. 1 and No. 2,
which are fed the command signals from the ground that are picked up
by the VHF antenna. Decoded instructions go to the command switching
control, which operates relays to turn equipment on or off. Reports
on the operation of this control are sent back by telemetry to the
ground station along with information from the satellite’s
sensors._]
VHF antenna
diplexer
command receiver No. 1
command decoder No. 1
T1 command
command receiver No. 2
command decoder No. 2
T2 command
command switching control (operates relays)
S-SS relay
D-DD relay
other relays
136-mc beacon transmitter
SS open
S close
telemetry
DD open
SS open
D close
sensors (radiation detectors, particle counters, solar aspect cells,
thermistors, etc.)
power supply
solar cell power plant
storage battery power plant
SS open
S close
through other relays to communications circuits and orientation torque
coil