If a port is configured for telemetry and OPLink is enabled, no telemetry data is sent if the OPLink modem is disconnected.
I've set up my Revolution to send telemetry to minOPOSD via the receiver port. I have OPLink configured as well. In this scenario, if the OPLink mini modem is disconnected while the Revo is boting, minOPOSD will not receive any telemetry data. It looks like telemetry data is sent only if OPLink is able to establish a link during boot.