Transmit Allow Timer

By default, the SRS-4 will automatically key up and transmit all frames that are routed for transmission on the space link interface. This default behavior can be changed using the tx.allow.always (default true) and tx.allow.time (default 0) properties.

Each second, tx.allow.time is decremented if its value is greater than 0. Before each transmission of a frame (normal or idle), the SRS-4 will check these properties and only allow the transmission if either tx.allow.always is true or tx.allow.time is greater than 0. If neither of these conditions are met, the frame is dropped.

To always boot in an inhibited state, the tx.allow.always property can be saved with a value of false in the boot and/or fallback stores. In the beginning of a pass, tx.allow.time can then be set to a value greater than 0 to allow transmissions during the pass. The figure below illustrates how the time can for example be set once in the beginning of a pass, or set periodically during the pass, similar to a watchdog timer. The tx.allow.time can always be set to 0 to disable the transmission as soon as possible.

../_images/txallow.svg

The tx.allow.time can not be stored and will always initialize to 0 on startup.