ISDN (Integrated Services Digital Network) connectivity is a faster form of dial-up access. It is a set of communication standards designed to digitally transfer voice, video, data and other network services over traditional telecommunication network infrastructure. The key feature of ISDN is that it itegrates data and voice over the same lines.

It typically provides 64 kBits/s or 128 kBits/s for both upstream and downstream connections. The performance of an ISDN connection is significantly better than that of a dial-up connection.

A special ISDN modem is required to connect to the ISP. The client will be billed based on the duration of the connection at normal call rates by the telecommunications provider (Telkom), as well as a premium rate for the monthly line rental. The ISP subscription remains a fixed monthly fee, also charged at a higher rate. Fixed monthly charges will vary depending on the speed of the connection (64 kBits/s vs. 128 kBits/s).

Telephone calls can be made on the line while the connection is active, with a second voice line being available when no connected to the internet.

This type of connection is preferred by users with low internet utilisation requirements, where the available of voice calls are more essential. The ISDN telecommunications infrastructure is more frequently available in rural or remote areas than broadband infrastructure, making it a more viable alternative for affected businesses than a dial-up connection.