User's Manual

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.
Monitor Polarity- The monitor input is used to override the action of the receiver squelch (mute) when
squelch is active. This function sets the polarity, active low or active high, of this input. When active,
squelch is disabled, even is enable via the Squelch Enable setting above.