Wireless transmission system used for a self-locking lock box

A wireless transmission system used for a self-locking lock box combined with a door body, said door body comprising a door plank and a door frame disposed at a circumference of said door plank, said door frame provided with a first insert hole corresponding to said door plank, said wireless transmission system comprising:

• a self-locking lock box installed at said door plank and formed with a housing, said housing bored with a first through hole corresponding to said first insert hole, a square bolt sliding in said first through hole, said square bolt connected with a square bolt spring, letting said square bolt have prestress to move out of said first through hole, said square bolt formed with a stop part, said housing having a control hole, said control hole received therein with a sliding control pin, said control pin able to slide along said control hole, said control pin protruding out of said control hole to form a stop position, and retracting back to said control hole to form a release position, said control pin blocking said stop part to make said square bolt impossible to eject out of said first through hole when said control pin is at said stop position, said control pin getting away from said stop part to permit said square bolt to be elastically pushed by said square bolt spring and eject out of said first through hole when said control pin is at said release position, said control pin connected a control pin spring, letting said control pin have prestress to move toward said stop position;
• a first transmission unit received in said first insert hole of said door frame, said first transmission unit provided with a first RFID coil facing outside of an opening of said first insert hole, said first transmission unit further provided with a control module, said control module electrically connected with said first RFID coil for controlling said first RFID coil;
• and
• a second transmission unit installed at a front end of said square bolt, said second transmission unit provided with a second RFID coil facing said first transmission unit, said second transmission unit disposed with a second control module, said second control module electrically connected with said second RFID coil for controlling said second RFID coil;
• Thus, said control pin pressed by said door frame and shifted to said release position to get away from said stop part when a user closes said door plank, and then said square bolt elastically pushed by said square bolt spring to eject out of said first through hole and get into said first insert hole, thus enabling said first transmission unit to approach said second transmission unit to shorten a distance between said first RFID coil and said second RFID coil for elevating transmission efficiency between coils.