The Universal Service Obligation is an obligation which can be imposed upon the dominant telecom operator (usually the incumbent). This obligation includes a demand to meet any request for provision of a particular telecom service to anybody within the country. The purpose of having such an obligation is to ensure national coverage of a particular telecom service also in remote rural areas, where provision of telecom service may become less profitable.
Most often USO includes provision of PSTN services only, but some countries include more advanced services as well. In Denmark ISDN and leased lines with a capacity up to 2 Mb are included in the USO, and within the EU it has been considered to include broadband services. In many developing countries, it is too ambitious to demand a universal provision of PSTN in all parts of the country and the USO may be replaced with a less demanding obligation of universal access. Universal access can be defined for instance as provision of at least 10 working phones in a certain area, as it is done in Bhutan.
A universal service obligation may include some price regulation in order to ensure affordability or a non-discrimination clause demanding that rural areas are provided telecom services under conditions similar to those applied in other areas.