While pairing the Arrow and Arrow+ models together is not officially supported, it can be done on some occasions. Official support cannot be offered for this configuration, but information about the process can be found below.
Pairing an Arrow transmitter with an Arrow+ receiver
This may work by downgrading the Arrow+ receiver to the standard Arrow firmware via the Paralinx Manager. However, you will not have multicast functionality in this configuration because of the transmitter's limitation.
Pairing an Arrow+ transmitter with an Arrow receiver
This configuration will not work, as the Arrow+ transmitter uses a new set of Multicast hardware that isn't compatible with the original Arrow receivers. Downgrading the Arrow+ transmitter firmware to Arrow firmware is likely to cause functionality issues with the device.