One of the most established and well-known standards for packet switched networks are the international standard X.25, The X.25 Recommendation defines the interface requirements between the user equipment (such as a terminal, bridge, router, and computer) and a packet switching network for data exchange X.25 network provides an efficient way to transfer data within one region, the country and even all over the world. The synchronous data transfer with a speed of up to 64 Kbps. The X.25 standards provides automatic error detection and correction, which allows X.25 networks to work effectively even in regions where the quality of communication lines is low. The X.25 interface provides Access to the remote user to the host computer (host). The X.25 standard describes the interface between the data entry equipment – DTE (Data Terminal Equipment) and data network equipment – DCE (Data Circuit terminating Equipment). Bridges, routers, terminals, personal computers (PCs), workstations are an example of equipment that can function as a (DTE) . When it is connected to a packet switched network. DTE provides the user part of the user-network interface. The equipment to which the DTE is connected is called DCE. DCE provides the network part of the user-network interface. Each DTE has its own DCE. However, several DTE devices can be connected to the same DCE. DTE-DTE connection is invalid; communication is only possible between DTE-DCE and DCE-DCE