DTMF-Code controlled lock device

DETAILED DESCRIPTION It is accordingly a primary object of the present invention to provide a DTMF-code controlled lock device that overcomes the foregoing problems associated with the prior art.
According to the present invention, this and other objects are achieved by the provision of a DTMF-code controlled lock device which comprises two main portions: a key control means having a structure adapted for being carried by a user and a lock-body control means adapted for being installed in a door together with a door lock.
The key control means is composed of a DTMF encoding circuit serving as a central part and having a keyboard coupled therewith for inputting a preset unlocking DTMF code therefrom, an amplifying circuit connected thereto for amplifying the DTMF signals and producing a DTMF tone through a sound generating means coupled with the amplifying circuit, and a conductive cord electrically connected to the DTMF encoding circuit for being used to perform unlocking operations.
The lock-body control means comprises: a transducing means adapted to be installed at a hidden place in a door for receiving the DTMF tone from the key control means; a pair of amplifying circuits connected in series to the transducing means for amplifying the DTMF signals; a telephone interface circuit coupled with one of the amplifying circuits for effecting unlocking operation through a key telephone set in case the key control means is not available; a decoding circuit coupled with the amplifying circuits for decoding the amplifed DTMF signals into BCD codes; a CPU with a plurality of memory units connected to the decoding circuit for receiving and identifying the BCD codes; and a pair of relay circuits respectively coupled with the CPU and the lock bolt for performing unlocking operations according to the controlling signal from the CPU; thereby, unlocking operations can be safely effected through the pre-arranged unlocking code input by the user so as to ensure complete security against unauthorized unlocking actions