Telnet

^ strg-altgr-9<enter> q<enter>

ssh

<enter> und dann

~.      Disconnect.
~^Z     Background ssh.
~#      List forwarded connections.
~&      Background ssh at logout when waiting for forwarded connection / X11 sessions to terminate.
~?      Display a list of escape characters.
~B      Send a BREAK to the remote system (only useful for SSH protocol version 2 and if the peer supports it).
~C      Open command line.  Currently this allows the addition of port forwardings using the -L, -R and -D options (see above).  It also allows the cancellation of existing remote port-forwardings
 using -KR[bind_address:]port.  !command allows the user to execute a local command if the PermitLocalCommand option is enabled in ssh_config(5).  Basic help is available, using the -h option.
~R      Request rekeying of the connection (only useful for SSH protocol version 2 and if the peer supports it).