Secure Shell (SSH) with only telnet proxy connection?

My workplace only allows http, ftp, telnet, and e-mail through its
firewall -- other protocols (ICMPs) are not supported.  Desiring a
secure channel to Community Connexion, does anyone know if there's a
way I could use, say, SSH (the Secure Shell) with only a telnet
connection?  Alternatively, is there a secure version of telnet
available?

I should mention that, via the firewall proxy, I can connect to any
port that I wish on the destination machine.  However, I still have
the standard telnet restrictions (i.e., the funny protocol, 7-bit
only, etc.), so my range is limited.

Thanks for any tips.

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