EQUIPMENT MANUAL 251-16-1
251/251-16-1
Page 3
The amplifiers are adjusted for acceptable listening output levels into the proper loads with ADF
receiver inputs of 7.75 V
RMS
, stereo audio inputs of 0.45 V
RMS
, PSC, TV, and Briefer audio inputs
of 1.00 V
RMS
and PA MIC input of 0.25 V
RMS
. With the volume controls set to maximum volume
position, these inputs will provide 7.5 V
RMS
(28 watts) into 2 ohms at each speaker output. The
ADF receiver input levels are achieved when receivers are set for 100 milliwatts into 600 ohms. If
levels are greatly exceeded at any of the inputs, the audio will become distorted due to peak
clipping and audio bleedthrough will occur. However, the amplifiers will not be damaged.
2.0 SPECIFICATIONS
Input specifications are expressed in volts RMS, rather than milliwatts, to avoid any
misunderstanding.
INPUTS
:
ADF: Two individual, switched audio inputs for ADF1 and ADF2.
Input level is 7.75 V
RMS
.
PSC: One switched audio input compatible with the Pilot Select COMM output of
dB Systems cockpit audio control amplifiers (such as Models 438 and 700), which
provides a 1.00 V
RMS
signal produced from a summation of selected COMM,
DME and MKR receivers. The PSC input can also be used for TV audio or other
similar audio.
TV: One switched audio input for TV (or other device). Input level is 1.00 V
RMS
.
STEREO
LEFT: One switched differential audio input for the left audio channel from an
AM/FM Stereo receiver/tape or CD deck (or other device). Input level is maximum
0.45 V
RMS
(at maximum source volume) and audio LO is not common to that
of other inputs.
STEREO
RIGHT: Same as stereo left, switched by the same control input as stereo left.
BRIEF: One switched audio input for automated cabin briefer audio. Input level is
1.00 V
RMS
.
PA MIC: The microphone input used for cabin paging audio supplies bias current and is
compatible with carbon and amplified dynamic microphones. Input level is
0.25 V
RMS
.
PAGING
VOLUME: Controls level of PA MIC and brief audio inputs to the PA sidetone and left and
right speaker outputs. Volume control range is 30 dB (minimum) controlled by
a 10,000-ohm, 1/2-Watt, linear pot. Maximum volume is with maximum resistance.
RECEIVER
VOLUME: Controls level of ADF, PSC and TV audio inputs to the left and right speaker
outputs. Volume control range is 30 dB (minimum) controlled by a 10,000-ohm,
1/2-Watt, linear pot. Maximum volume is with maximum resistance.
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