Remote access Netware 5.0 server

I would like to allow 10 of my collegues to remotely access an Netware 5 server. My collegues carry notebooks with PC Bus/ PC card modems of mixed brands. I have a US Robotic 56K Faxmodem connected to my Netware 5 server and Netware Connect 2,0 running on it. I discovered that this setup does not work very well as not all PC bus/ PC card modem is able to dial-in successfully. I need a solution that will give me 100% successful dial-in and maybe a not too expensive alternative that will give me better data transfer speed. Security must be taken into consideration.

Advise please.
Thank you.