Design and Construction Handbook - Los Angeles World Airports

Guide Specification
5. Absence of ground faults.
6. Polarity.
E. Use the proper sequence of energizing systems to minimize the risk of damage.
F. Sound Systems:
1. Electronic Tests; confirm:
PAGING SYSTEMS
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a. Gain at 1 kHz.
b. Maximum output.
c. Input clipping level.
d. Frequency response.
e. Total harmonic distortion.
f. Signal-to-Noise ratio.
g. Signal-to-Crosstalk ratio.
2. Gain control settings: Establish tentative normal settings for all gain controls. Set all
equalizers flat. Set all automatic gain control devices to bypass. Terminate power
amplifier outputs with power load resistors with resistance value within 10% the nominal
output impedance of the respective amplifier. Adjust all gain controls on equipment for
optimum signal to noise ratio and signal balance and, unless they are sub panel mounted,
cap them to prevent tampering. Unless specified or directed otherwise, adjust gains such
that in a given system the "front end" operates at unity gain and maintains 10 dB of clip
margin referenced to the first onset of clipping of the associated power amplifier(s).
Measure and document system gains at 1 kHz. Settings may require further adjustment
by the Contractor, a result of testing by the representative of the Owner.
3. Freedom from parasitic oscillation and radio frequency pickup: Maintain previous setup.
Set up for each mode of operation specified in the functional requirements; verify that all
systems are free from spurious oscillation and radio frequency pickup using broadband
oscilloscope. Correct any such defects.
4. Hum and noise level/signal to noise level/signal to crosstalk level: Maintain previous
setup. Terminate microphone and line level inputs with shielded resistors of 150 and 600
ohms, respectively. Set available variable gain controls such that full power amplifier
output would be achieved with 40 dBm input level at a microphone input and +12 dBm at
a line level input. Measure and document the specified parameters of the system overall
for each microphone input channel and line level input channel. Compare with nominal
signal level.
Communication Systems