Netscape-7: adding protocol helper for TELNET

Hi,

I am running Netscape version 7.0 on Solaris-9, and have problems 
finding out how to add a mechanism for the TELNET protocol (and other 
protocols, like SSH) when I want to use URLs in the form

telnet:somehost

or

telnet://somehost/

(same for 'ssh')

on Netscape v4.x, everything was pre-configured to support non-HTTP 
protocols, they are initiated nicely in a new terminal window.

But in NS v7 there is no way provided in the GUI to add ("register") 
protocols :

Edit -> Preferences -> Navigator -> Helper Applications

is the only menu that's more or less relevant, only that there is no way 
to add a URL method.
When adding a new entry in the list (with "New Type"), the only fields 
you can specify is "MIME Type" (anything known for TELNET, SSH, ...?), 
file extension (sure not relevant!), and application (this would be my 
'ssh' client program, intended to be launched inside a new terminal window).

Anyone has a suggestion or link to more information?

Many thanks in advance,

R. De Langhe
Belgium