6, Automatic Switching Unit Rack 2 
f, "“Low-speed" (S5mm/sec.) PL Sound Level Rack 2 
Recorder 
Bo Magnetic Tape Recorder, 1 Rack 3 
h. "High-speed" (10mm/sec.) PL Sound Level Rack 3 
Recorder 
i, Magnetic Tape Recorder 2 Rack 2 
jo Chronometer and code switch - - Rack 3 
OPERATING THE SOFAR HQUIPMENT BEFORE A SIGNAL IS RECEIVED 
28, Turn on all AC power switches. These are the master switch on the 
front of Rack 1; a switch om each of the 7-volt power supplies in the back 
of Rack 1\ on the second snd third sheives from the bottom; a switch on 
the automatic switching device on the top shelf of Rack 23 a switch on 
each PL sound level recorder on the second shelf from the top of Rack 2 
and 33 and a switch on esch magnetic tace recorder on the second shelf 
from the bottom of racks two and HI 
29. To prolong the useful life of the selenium rectifiers in the amplifier 
channels, the channel which is not in use should be turned off by means of 
_the switch at the rear of the 7=-volt DG supply for this particular channel 
(the supply for channel one is on the right side of the third shelf from 
the bottom of Rack 1, and the supply for channel two is on the right side 
of the second shelf from the bottom), 
30, Similarly, to prevent wear and consequent dulling of the pole pieces, 
the stand—by magnetic recorder. shouid be turned off, The Western Electric 
‘Mirrophone magnetic tape recorder is turned off by rotating its 3KC. V.C. 
completely counterclockwise, and the Caltron magnetic tape recorder is 
turned off by rotating its siG. 7.C, completely counterclockwise. - Normally, 
the magnetic tape and Power Level recorcers in Rack 3 are kept on stand—by. 
However, the Power Level recorder in Rack 3, which is identified as the “high- 
speed" recorder, may be used to transcribe the sound record from either of 
the magnetic tape recorders. This recorder operates at a paper—bape speed 
of 10mm/sec, which will double the time indexing space and give an accurate 
check on the arrival time evaluation, 
31. Under normal continuous long-term operation the operator should establish 
a rotation cycle so that the duty load can be divided among the duplicate 
parts of the equipment, This rotation will prolong the efficient operation 
of both types of recerding equipment and of the power supplies and amplifier 
channels, 
