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USER MANUAL FOR HARDWARE REV 3.11
07-APR-2018
PAGE 6
3.1.4
FLAT AUDIO SELECT
This is use to select if the audio coming in requires the addition of a flat-audio filter (removes pre-
emphasis). To enable the addition of the flat audio filtering, the switches should be in the down
position (towards the USB/ETH jacks on the PI).
To pass the audio unfiltered, the switches should be in the up position as shown in the figures above.
To learn more about “Flat Audio” we recommend starting here:
http://www.repeater-builder.com/tech-info/flat-audio.html
3.1.5
OUTPUT AUDIO ADJUST
The output audio adjust is used to adjust the amplitude of the volume coming from the repeater board.
This is an multi turn, 10kΩ potentiometer, multiple turns are required to effect a large change in
amplitude, while fractional turns yield fine resolution adjustments.
This function is used to adjust the amplitude of the repeated audio being sent to your transmitter radio.
This output amplitude should be adjusted per the transmitter radio specifications.
3.1.6
CTCSS ACTIVE HIGH/LOW
This switch is used to select the active on state for the CTCSS signal from the receiver radio. Typically
this will be active low, but some radios output an active high signal.
When using active high signaling, the input will trigger above 1.25V and will release when the signal
returns below 0.6V.
When using active low signaling, the input will trigger below 0.4V and will release when the signal
returns above 0.7V
3.1.7
COS ACTIVE HIGH/LOW
This switch is used to select the active on state for the COS signal from the receiver radio. Typically this
will be active low, but some radios output an active high signal. This input can be used for 3-18Vdc
signal levels.
