GAI-Tronics 69439-001 External Audio Interface (EAI) - Manual (Page 8)

Pub. 42004-677L2C
Model 69439-001 External Audio Interface Page: 8 of 9
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Frequently Asked Questions
Q: When the card rack is powered, but the MCU is either not installed or not properly configured, is
there some feature of the EAI that can aid in determining if a connection to one of the audio inputs is
properly wired?
A: Yes. The bottom four LEDs, labeled AUD IN #1 , AUD IN #2 , AUD IN #3 , and AUD IN #4 , are
controlled by the EAI independently of the MCU. Each LED shows the detected audio status of the
600-ohm audio input corresponding to the LED’s label. After injecting a signal on a wire in question, one
can use the associated LED to tell if the wire is connected.
Q: Is there a common reason why one of the bottom four LEDs, labeled AUD IN #1 , AUD IN #2 , AUD
IN #3 , and AUD IN #4 , may never turn off?
A: Yes. The 600-ohm audio input corresponding to the LED might be detecting excessive noise. One
common cause of this excessive noise is a ground problem.
Q: Why are the levels on the audio outputs 6 dB higher than specified?
A: A 600-ohm resistor is not connected across the audio output.
Q: Must the resistor network be installed when using the contact input terminals?
A: Yes; if not, the system will report a fault condition.
Specifications
Electrical
Board
Power ................................................................................................ 575 mA maximum @ +5 V dc ±10%
150 mA maximum @ +12 V dc ±10%
150 mA maximum @ −12 V dc ±10%
1.0 kHz Sine Wave Detectors
N OTE : Use a card rack audio bus when measuring amplitude.
In-range frequency........................................................................................ (within) inside 1.00 kHz ±1%
In-range amplitude on card rack audio bus......................................inside 4.24 Vp-p (1.50 Vrms) ±1.5 dB
Out-of-range frequency............................................................................. (beyond) outside 1.00 kHz ±3%
Out-of-range amplitude on card rack audio bus.............................outside 4.24 Vp-p (1.50 Vrms)
±4.5 dB
600-Ohm Audio Input
Audio input voltage.................................................................................2.82 Vp-p (1.00 Vrms) maximum
Audio input to card rack audio path frequency response................................ 250 Hz to 12.0 kHz
±1.5 dB
Audio input to card rack audio path distortion + noise............................THD + noise <0.5% @ 1.00 kHz
Audio input impedance...........................................................................
≥24 kΩ from 250 Hz to 12.0 kHz
Audio detect level for LED.................................................................282 mVp-p (100 mVrms) maximum
Audio not detected threshold for LED..............................................28.2 mVp-p
(10.0 mVrms) minimum