A portable telephone communications device for the hearing impaired can be carried in the pocket of the user and attaches directly to the telephone handset without intrusion. It includes a keyboard and a readout which enables the user to transmit data by means of the keyboard and receive data which is...http://www.google.fr/patents/US4268721?utm_source=gb-gplus-shareBrevet US4268721 - Portable telephone communication device for the hearing impaired
Portable telephone communication device for the hearing impaired
