The PSTN/ISDNEmulation Subsystem (PES) is a control system in the NGN architecture, Next Generation Network
. The PES subsystem belongs to
theService Control Subsystems and provides for the emulation of analogue PSTN and digital ISDN. Analogue and digitaltelephony is connected to the All-IP network
ofthe Next Generation Network (NGN) via this subsystem.
The PES subsystem was specially developed to replace components that work with time division multiplex (TDM), while other terminals can continue to be operated unchanged.