GAI-Tronics 69439-001 External Audio Interface (EAI) - Manual (Page 3)

Pub. 42004-677L2C
Model 69439-001 External Audio Interface Page: 3 of 9
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Audio Inputs
The 600-ohm audio input 1, 600-ohm audio input 2, 600-ohm audio input 3, and 600-ohm audio input 4
provide four audio inputs to the system. These inputs may be independently routed to one of the
following five card rack audio busses: evacuation, page resource 1, page resource 2, party line 1, or party
line 2. The EAI is not able to mix audio sources, therefore only one audio input may be connected to a
particular card rack audio bus at a time. The EAI constantly checks for the presence of a signal on these
inputs and updates the state of its corresponding status LED mounted on the front panel.
Figure 2. Typical audio input connection
Audio Outputs
The 600-ohm audio output 1 and 600-ohm audio output 2 provide two audio outputs from the system.
These outputs may be independently routed from one of the following four card rack audio busses: page
resource 1, page resource 2, party line 1, or party line 2. The EAI is not able to mix audio sources,
therefore only one card rack audio bus may be connected to a particular audio output at a time. Each
audio output requires an external 600-ohm load resistor for proper operation.
Figure 3. Typical audio output connection
N OTE 1: The audio output “shield” terminal is coupled to ground by an internal capacitor on the EAI
card. This is done to suppress any high frequency noise, which may be induced on the cable. Do not add
any external capacitors when terminating the cable shield.