A trainable transmitter includes code generation circuitry and a socket for receiving a plug-in module including circuitry for generating an RF signal. By selecting the appropriate plug-in module, the user can expand the frequency transmission range of the transmitter beyond that which may be pre-installed...http://www.google.fr/patents/US6333698?utm_source=gb-gplus-shareBrevet US6333698 - Expandable multiple frequency programmable transmitter
Expandable multiple frequency programmable transmitter
