That blinking red light!

If you've ever swapped control heads on a DM4000 series mobile, you might have encountered this symptom at least once. The radio works normally otherwise, it's just that the red LED (pictured above) blinks continuously. This could also occur if you've fitted a handheld control head or remote mount kit (pictured below).

The root cause is that the firmware in the control head does not match that which is in the radio. When the radio is produced or upgraded, both the radio and control head get written with some firmware.

Swapping or replacing the control head sometimes means that the firmware could get out of synch (e.g. new replacement control head on an old radio).

The fix is to perform a device recovery. This essentially rewrites the firmware and default codeplug to the radio. Don't forget to read and save the codeplug in the radio before doing this.

Device recovery is a CPS function. In addition to the CPS, in order to do a device recovery, you will also  - ideally - need the firmware package used in that radio. If you don't have that, the latest (or a newer-than-what-you-have) version will also do.

In some cases, certain premium features (licenced features) may be lost when doing a device recovery (e.g. Capacity Max). This is not a problem as radio licences can be recovered using the CPS or Radio Management.