ISDN stands for Integrated Services Digital Network. ISDN makes it possible to send, receive and modify information using telephone lines with speed and quality that were not previously possible. Currently, ISDN is the only digital technology that can be accessed worldwide. High-speed serial ports with compression can support throughput speed of 230 Kbps and higher.

ISDN is not an application itself; it's really a technique that works to augment applications. For instance, some individuals who work at home and need access to their corporate LAN or the Internet find that accessing these services is slow and cumbersome when using a 28.8 Kbps and 56 Kbps modems. With ISDN, data speeds of 64 Kbps or 128 Kbps, and access to their department LAN, the work-at-home client can have all of the access and privileges as their peers in the office.

Qwest Single Line Service is the brand name for ISDN Basic Rate Service. ISDN Single Line Service's standard package includes a comprehensive 2B + D bundle that delivers numerous voice and data features.

ISDN Single Line Service (SLS) is a platform-based, switched digital service offering fast, flexible, highly reliable and digitally clear connections with the simplicity of dialing a telephone. Based upon international communications standards, ISDN provides users the access to the powerful capabilities of today's Public Telephone Network for communicating across town or around the world.

ISDN Single Line Service uses the existing pair of wires that now delivers the one communication-at-a-time basic phone service to business or residence customers. SLS now provides, over those existing pair of wires, two primary high speed (64 Kbps) communications channels that can be used simultaneously or independently to carry any combination of data, image, video or voice calls. Users of ISDN can combine these two channels to achieve a data transfer rate of up to 128 Kbps. SLS also provides a third channel known as the 'D' channel for low speed data communications, ideal for point of sale, remote monitoring or telemetry applications.

No special handling is required when voice calls are made between ISDN phones and conventional telephones – the network manages the necessary conversions. When conducting data calls, in order to utilize the B Channels for digital communications, digital equipment is required at both ends of the communications path, as is the case with conventional modem connections or fax machine transmissions. Most ISDN modems have analog ports for modem-to-modem communications, providing the ISDN subscriber the best of both worlds!