serial bridge encrypted with Portserver TS MEI?

we have two Portserver TS 1 MEI and are using them in serial bridging mode.
The Product documentation mentioned, that it is possible use ssh-based encryption.
But it’s not clear wether a serial bridge connection is encrypted or not per default, or even if it’s possible.
Because one end of the connection is a POS-Terminal with legacy OS and the other end is a 2400 baud modem, we cannot use the Realport-Feature of the Portserver.
Any suggestions?

THX Dirk

Since, the PortServer products only provide the ssh server (not client), encrypting a serial bridge is not possible.