A Public access branch exchange is a smaller phone exchange that is used by one company or in one building. The PABX is owned or rented by the company. The reason for using a PABX is that in a company that has more than a few employees it would be expensive to get single phonelines to every phone. The PABX makes it possible to call from one phone, connected to it, to another without using the public phone system, thus saving money on the phonebill. Also internal numbers are shorter. Modern PABX'es offer many spesial services like the possibility to connect wireless phones and automatically transfer calls. Some can even be interconnected over leased lines and act as one. This means a company that is spread over a large geographical area can use short numbers.