Automatic telephone line sharing apparatus is disclosed that will only allow one telephone set or other communication device to be connected to a shared telephone line at a time. Circuits in the apparatus sense when a first one of a plurality of telephone sets or other communication devices is connected...http://www.google.fr/patents/US4805210?utm_source=gb-gplus-shareBrevet US4805210 - Automatic telephone line sharing and lockout apparatus
Automatic telephone line sharing and lockout apparatus
