Signal transmitter, message generating system and signal power adjusting method

A message generating system communicating with at least one mobile device through a communication network, wherein the message generating system comprises:

• a management module;
• a message transmitting module electrically connected with the management module;
• and
• at least one signal transmitter with adjustable signal power, wherein each of the at least one signal transmitter comprises a first adjustable metal shielding layer and a circuit board, the area of the first adjustable metal shielding layer consisting of a first shielding area and a first un-shielding area, wherein the first shielding area and the first un-shielding area are adjustable, and the circuit board is configured for adjusting signal emission power to emit a signal according to the first un-shielding area of the first adjustable metal shielding layer;
• wherein the at least one mobile device transmits device information to the management module according to the signal emitted by the circuit board of the at least one signal transmitter, the management module stores apparatus information of the at least one signal transmitter and a corresponding message, and when the management module receives the device information transmitted from the mobile device, the management module controls the message transmitting module to transmit the corresponding message to the mobile device according to the apparatus information corresponding to the device information.