ISDN dial-on-demand internet by Bluetwo IT Solutions. ISDN is a dial-on-demand Internet connectivity solution. It offers you a hassle free, simple and effective way to connect a LAN to the Internet with a high-speed ISDN line. Internet is accessed when any user opens their browser or their e-mail. Unlike a permanent leased line, the Telkom cost of the ISDN line is dependent on the amount of time spent on the Internet or its related products (e-mail, ftp etc).