El proveedor de la red telefónica activa un grupo de líneas de centralita privada RDSI en el conmutador telefónico y permite llegar a varias conexiones RDSI punto a multipunto bajo un solo número de teléfono. Las conexiones RDSI están técnicamente interconectadas a una única conexión virtual. Combinando tres conexiones punto a multipunto, por ejemplo, el abonado dispone de hasta seis canales B para llamadas paralelas. Dependiendo de la conexión y de la red telefónica, las llamadas entrantes se indican alternativamente o simultáneamente. La disponibilidad de características de conveniencia puede estar limitada con este tipo de conexión.
By setting up an private branch exchange line group on a telephone system, several extensions can be reached under a single telephone number. The telephone system can route incoming calls to free extensions. The type of private branch exchange line group being used determines how calls are routed. One option is cyclical routing, where incoming calls are routed equally among all extensions. A hierarchic routing will route the call to the first free extension. The "Block private branch exchange line group" feature allows individual extensions to connect or disconnect from calls through the online service.
The private branch exchange line group function has also made its way into Voice-over-IP telephony and network-based cloud telephone systems. Many systems allow the user to sign into an online service or a premium service number with queue right from their phone. This can be done regardless of the actual location and only requires an internet connection. The connection can be static or mobile. Call logs will then show if calls are e.g. coming from an private branch exchange line group or a queue.