The invention relates to telecommunication equipment (10) for setting up local telephone calls between GSM mobile telephones (1) of a private network, on the one hand, and a public GSM mobile telephone network (5), on the other hand. The equipment includes connection means to the public network and connection means to each mobile telephone of the private network. For the connection to the public network, it includes a downstream radio access system (3) for access to radio base transceiver stations (5) of the public network. For the link to the mobile telephones (1) of the private network it includes upstream radio access system (2) conforming to the GSM standard, like the public network. The equipment further includes a service signal converter module (4) between the upstream system (2) and the downstream system (3).