A security monitoring system for a building or a secured space within a building, the system being operatively connected to a monitoring station, the system including: a control unit for controlling, arming and disarming the security monitoring system, and having a first radio frequency transceiver which can support a first maximum bitrate, and a second radio frequency transceiver which can support a second maximum bitrate lower than the first bitrate, and a controller for controlling the radio frequency transceivers (230, 232); a camera node having a node controller; an image sensor for capturing images; a primary node radio frequency transceiver, for communication with the control unit; a secondary node radio frequency transceiver, to receive control messages from the control unit, the primary node radio frequency transceiver supporting a higher maximum bitrate than the secondary node radio frequency transceiver; the node controller of the camera node being configured to: transmit both a captured image with a first image ID as a first image file using the primary node radio frequency transceiver and as a second image file using the secondary node radio frequency transceiver, the first image file having a higher resolution and a larger size than the second image file; the node controller being further configured, in the event that an acknowledgement of receipt is received for the reception of the second image file but not for reception of the first, to resend the first image file using the secondary transceiver; the control unit being configured, on reception of the first to arrive of the first or second image files, to transmit the first arrived file to the monitoring station, and thereafter, if the first arrived file was the second image file, on arrival of the first image file, to transmit the first image file to the monitoring station. a control unit for controlling, arming and disarming the security monitoring system, and having a first radio frequency transceiver which can support a first maximum bitrate, and a second radio frequency transceiver which can support a second maximum bitrate lower than the first bitrate, and a controller for controlling the radio frequency transceivers (230, 232); a camera node having a node controller; an image sensor for capturing images; a primary node radio frequency transceiver, for communication with the control unit; a secondary node radio frequency transceiver, to receive control messages from the control unit, the primary node radio frequency transceiver supporting a higher maximum bitrate than the secondary node radio frequency transceiver; the node controller of the camera node being configured to: transmit both a captured image with a first image ID as a first image file using the primary node radio frequency transceiver and as a second image file using the secondary node radio frequency transceiver, the first image file having a higher resolution and a larger size than the second image file; the node controller being further configured, in the event that an acknowledgement of receipt is received for the reception of the second image file but not for reception of the first, to resend the first image file using the secondary transceiver; the control unit being configured, on reception of the first to arrive of the first or second image files, to transmit the first arrived file to the monitoring station, and thereafter, if the first arrived file was the second image file, on arrival of the first image file, to transmit the first image file to the monitoring station. transmit both a captured image with a first image ID as a first image file using the primary node radio frequency transceiver and as a second image file using the secondary node radio frequency transceiver, the first image file having a higher resolution and a larger size than the second image file; the node controller being further configured, in the event that an acknowledgement of receipt is received for the reception of the second image file but not for reception of the first, to resend the first image file using the secondary transceiver; the control unit being configured, on reception of the first to arrive of the first or second image files, to transmit the first arrived file to the monitoring station, and thereafter, if the first arrived file was the second image file, on arrival of the first image file, to transmit the first image file to the monitoring station.