Abstract: A radio-signal-based mail delivery alarm system comprising a transmitter unit provided in connection with a mailbox or mail-slot flap (2) and a receiver unit for being located at a distance from the transmitter unit and being able to receive a radio signal emitted by the transmitter unit. The transmitter unit comprises a movement sensor for detecting movement of the mailbox or mail-slot flap (2) and a transmitter with power supply and antenna (12) for emitting a radio signal in response to movement of the mailbox or mail-slot flap (2). As opposed to the prior art transmitter units for such mail delivery alarm systems, the present transmitter unit is built integrally with the mailbox or mail-slot flap (2).

Abstract: A receiver unit (2) for a radio signal-based mail delivery system comprising a transmitter unit (1) for being mounted on a mailbox or mail slot flap (4) and such receiver unit (2) for being located at a distance from the transmitter unit (1). The reciver unit (2) is provided with a receiver for receiving a radio signal and with means for indicating that such radio signal has been received. Besides, the receiver unit (2) is provided with a clock and is configured for registering the hour when the radio signal was received; and the means for indicating when a radio signal was received comprise a visual and/or audible message about the hour when the radio signal was received also including a mail delivery system comprising such receiver unit.