CalAmp Viper 100 User Manual page 50

― Enabled (listen to noise and data). Viper listens on the Rx frequency and determines if the RF channel is available.
Channel is available so long as received level is higher than the carrier sense threshold. When the channel is busy, Viper
receives and decodes all remote messages Data is buffered and sent when the channel becomes available.
Received level is above the carrier sense threshold if:

Viper is receiving valid data

Viper is not receiving data because two or more Viper SCs are transmitting at the same time causing a collision

Viper is not receiving data because the RF level is right at or below data sensitivity or

There is interference from another RF system or electrical devices on the frequency that Viper is operating on.
― Enabled (listen to data only). Viper SC will monitor the RF level on the receive channel. When the received level is
above the carrier sense threshold, Viper SC will try to receive and decode any and all messages from remote Viper SCs.
When data is ready to transmit, Viper SC will first check the receive level. If the receive level is below the carrier sense
threshold, Viper will immediately transmit data. If the receive level is above the carrier threshold, Viper will try to
determine if it is receiving valid data or just noise. If it is receiving noise, Viper will go ahead and transmit. If it is
receiving valid data, Viper will wait until the complete packet has been received before transmitting. Viper SC will
typically takes 5-250 ms to determine if it is receiving valid data or just noise.
― Disabled. Viper will attempt to receive/decode data when the received RF level is above the carrier sense threshold.
When the Viper SC has data to transmit it will immediately transmit the data. The Viper SC will immediately stop
receiving any packets and will transmit over any other Viper SCs that are on the air and over any interference that may
be in the area. This mode should only be used in a polling type environment where the user has strict control over the
traffic that is generated.
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