OPTIMOD-FM
The power supply circuits are straightforward and no explanation is required beyond the
schematic itself. Be aware that C19, C50, C52, and C53 in the switching regulator are
premium-quality low-ESR capacitors and must be replaced with equivalent types to en-
sure proper operation of the switching supply.
The output of the power supply is monitored by the power-indicator LED circuit, which
causes the power LED to flash according to a preset code to diagnose problems with the
various power supplies in the 8400. See step (2.B) on page 4-10.
Abbreviations
Some of the abbreviations used in this manual may not be familiar to all readers:
A/D (or A to D)
analog-to-digital converter
AES
Audio Engineering Society
AGC
automatic gain control
A-I
analog input
A-O
analog output
BAL
balanced (refers to an audio connection with two active conductors and one shield sur-
rounding them).
BBC
British Broadcasting Corporation
BNC
a type of RF connector
CALIB
calibrate
CIT
composite isolation transformer
CMOS
complementary metal-oxide semiconductor
COM
serial data communications port
D/A (or D to A)
digital-to-analog converter
dBm
decibel power measurement. 0 dBm = 1mW applied to a specified load. In audio, the load
is usually 600Ω. In this case only, 0 dBm = 0.775V rms.
dBu
decibel voltage measurement. 0 dBu = 0.775V RMS. For this application, the dBm-into-
600Ω scale on voltmeters can be read as if it were calibrated in dBu.
DI
digital input
DJ
disk jockey, an announcer who plays records in a club or on the air
DO
digital output
DOS
Microsoft disk operating system for IBM PC
DSP
digital signal processor (or processing). May also refer to a special type of microprocessor
optimized for efficiently executing arithmetic.
EBU
European Broadcasting Union
EBS
Emergency Broadcasting System (U.S.A.)
EMI
electromagnetic interference
ESC
escape
FCC
Federal Communications Commission (USA regulatory agency)
FDNR
frequency-dependent negative resistor⎯an element used in RC-active filters
FET
field effect transistor
FFT
fast Fourier transform
FIFO
first-in, first-out
G/R
gain reduction
HF
high-frequency
HP
high-pass
IC
integrated circuit
IM
intermodulation (or "intermodulation distortion")
6-13
TECHNICAL DATA
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