digital wireless radio transmitter/receiver consists of a 4x4 keyboard that can be used to typing a PIN to send to the receivers, All PINs are stored in non volatile EEPROM memory both in the transmiter and receiver. The device was made using STM32F051R8T6 microntroller , nRF24L01+ radio transceivers, AT24C64D eeprom memory and it's powered by the FREERTOS - real time operating system for embedded devices (www.freertos.org)