TX Pre-emphasis- Allows for the signal path from AUX IN and the MIC IN input to be either pre-
emphasized or flat. Most applications where the AUX IN input is used work best with a flat
response. Factory default is flat response.
RX De-emphasis- Allows for the signal path from the discriminator to the AUX OUT and Audio
Out to be either de-emphasized or flat. Most applications where the AUX OUT output is used
work best with a flat response. Factory default is for flat response.
Busy Channel Lockout- Prevents the transmitter from activating when the carrier detect output is
true. Used to prevent interference on a channel where activity already exists. Not normally
enabled in half duplex operation since the transmit and receive channels are not on the same
frequency. Factory default is for this function to be off.
Squelch Enable- Allows the receive audio paths to be muted when the carrier detect output is
false. It is used to prevent the output of noise from the audio outputs when no signal is present.
Due to the finite squelch attack time, some high-speed modems work best with unsquelched
audio. The factory default is for this function to be set for never mute.
DCD Output Logic Level- Allows the setting of the polarity of the DCD (Data Carrier Detect)
output. Active high means that the true state is a logic high while active low means that the true
state is logic low. Normal setting is active high. The factory default is active high.
Microphone Gain- Available when the Audio Input selection is set to Microphone. This box allows
the gain of the signal at the Microphone input to be set either low or high. Factory default is for
the Microphone input gain to be set to low. Note that if the Audio Input is set to AUX IN above, no
signal from the Microphone input will be passed to the transmitter.
Audio PA- Turns the AUDIO OUT output on or off. Turning the AUDIO OUT output off when not
needed saves current drain in receive.
RX Discriminator Coupling- Selects whether the coupling from the discriminator output on the RF
board is AC or DC coupled to the control/loader board. Since the audio outputs of the
control/loader board are AC coupled, this function is normally set for AC as well. Setting this
function to DC will extend the low frequency receiver response somewhat, but makes the audio
output subject to clipping due to DC offsets on the discriminator output. For true response to DC,
a hardware jumper options can be made for DC coupling at the AUX OUT. (See the Hardware
Options section under Maintenance for details on this option.) If this is done, this function should
be set for DC. For direct-modulated type of data streams such as true FSK, RRCFSK, 4FSK, etc.,
DC coupling may be indicated, even if the output of the unit is not modified for true DC coupling to
the output. AFSK modulation types such as Bell 202, etc. should use AC coupling. The factory
default is AC.
CSN Input- Selects whether RNET Compatibility mode is to be used. See section 5.6 for an
explanation of this function. Normal operation is to set this for high/low Power. The factory
default is high/low power mode.
High Pass Filter- When RX Discriminator Coupling is set to AC, this box is enabled. This box
allows a choice of two rolloff frequencies for the lower high-pass rolloff. The 250 Hz selection may
attenuate certain types of data signals and cause tilt on square waves, but is the fasted at
responding to changes in discriminator DC level caused by frequency errors on either the
receiver or the receiving transmitter. For better low-frequency response, 50 Hz may be selected.
CSN Input- Controls the function of the CSN pin. This pin can be used to select one of two
transmitter power levels in the High/Low Power position or can be used to select one of two
channels in the RNET Channel 1/2 mode. See Section 5.6, RNET COMPATIBILITY MODE for
details on this selection.
CTS Output Logic Level- Sets the polarity of the CTS (Clear-To-Send) output. Setting for active
high caused the true logic state to be high. Active high is the normal setting. The factory default
is active high.
