If the explosives are inside the battery how were they actually triggered? Some reports suggest they were triggered by a message sent to the pagers over the pa

If the explosives are inside the battery how were they actually triggered? Some reports suggest they were triggered by a message sent to the pagers over the pager network. But batteries generally are only connected to the power and ground lines of the device they are powering. If the pager firmware was modified to watch for receiving a special trigger how would the firmware communicate that to the explosives inside the battery? It would seem there would have to be some extra connection from the mainboard to the battery. I suppose there could be wireless communication between the mainboard and something inside the battery. I doubt a pager would feature Bluetooth, since you generally don't need headphones with a pager, but often devices use chipsets that include capabilities the device doesn't use. E.g., you might use an ESP32 module to give your device WiFi capabilities and completely ignore that ESP32 also can do Bluetooth. If the chipset has Bluetooth or some other radio communication support not used by the pager firmware, the bomb maker could have put a receiver for that in the battery with the explosive and hacked the firmware to use that. Actually, now that I think about it, maybe a firmware hack could communicate to something inside the battery over the power connection. There are probably things the firmware can do that affects power use, like changing the display brightness. It could do something like rapidly switch between maximum and minimum brightness in a particular pattern. A trigger inside the battery could watch power use and look for fluctuations that match that pattern.