CalAmp GUARDIAN User Manual download pdf (Page 39)

An end-of-transmission quiet period approximately 8 characters long can be invoked on the Guardian by holding its

transmitter on briefly after RTS is dropped. This quiet period (which occurs between the last valid data character and

any possible extraneous “noise” bits) may be of benefit to some DTE that would otherwise be adversely affected by the

extraneous bits.

Rx-Only Radio

The Rx-Only Radio option instructs the modem to receive data and diagnostics from other modems only. Enabling this

option disables user data delivery. The default value for this option is Disabled (unchecked).

Inverted Carrier Detect (CD)

Carrier Detect (CD) is a 0-5 VDC output that is triggered by the receiver squelch circuit when it senses a signal strong

enough to meet the carrier sense (CS) setting. In some applications, it is desirable to use the CD line to set another

radio to transmit or to control an external device by providing a ground. To accomplish this, the CD line would be

inverted to provide 5-0 VDC. The default value for this option is Disabled (unchecked).

Dynamic Carrier Detect Off Threshold

Allows the modem to automatically adjust the Carrier Detect Off Threshold based on the RSSI while receiving data. If

selected, the Carrier Detect Off level will automatically adjust to approximately 15 dB below the actual signal strength.

This provides rapid detection of loss-of-carrier and minimizes or eliminates “bit dribble” at the end of transmissions.

The default value is Enabled (checked).

Recommendation: Keep Dynamic Carrier Detect Off Threshold enabled (checked) unless interference or variable signal

strength (i.e., fading in a moving vehicle) causes problems.

Carrier Detect On Threshold

The sliding control allows the user to set the minimum RSSI level that the Guardian Modem will recognize as a valid

carrier and begin decoding data.

5.6.2 RF LINK

The RF Link panel provides the interface for programming various radio operating parameters.

Figure 20 RF Link Panel

Guardian™ Serial Modem or Analog Radio for Licensed Spectrum PN 001-5006-000 Rev. 3 | Page 31

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CalAmp GUARDIAN User Manual Page 39