If you give another callsign, either of a local station or a node, the node will attempt to connect you to that station either by a level 4 connection or by downlinking. If you are downlinking, you may also specify digipeaters.

In either case, you get either a connected message or a message telling you of the failure to connect. If you enter any other command at this stage, the connection attempt will be aborted.

If you attempt to downlink with digipeating, or attempt to downlink to an invalid callsign such as a node alias with an SSID, you may get an error message depending on how the Sysop has configured the node.

Finally, if you connect to the node, then connect to another station, and that station disconnects you ( e.g. connect to a BBS and use the 'Bye' command of the BBS ), you will either get reconnected to the node or disconnected completely depending on the configuration of the node.

If you enter a node alias and get an 'invalid call' message, it can either be because the node is not recognised or it can be because the Sysop has made node aliases case sensitive.