Comment by LeifCarrotson

Comment by LeifCarrotson 3 days ago

No, a pager is optimized to be a case size that's comfortable for carrying and reading. The electronics could be the size of the smallest wristwatch, which is already dominated by its own form factor requirements, not the PCB + battery + display subcomponents that are scarcely the size of a nickel.

A typical pager is about 60 x 40 x 20mm. Much of this volume requirement is driven by the 16mm diameter 34mm long CR123 battery, a lot of it could be empty.

That battery is a relatively safe lithium primary chemistry, not a rechargeable Lithium polymer pounch or lithium ion cylinder that would risk fire and explode if the overpressure vents were omitted and the BMS corrupted, but the primary lasts for years.

I bet you could use a CR1216 battery (1.6mm thin, 30mAh, instead if 34mm long and 1500mAh) instead and have quite a good deal of spare volume in the battery for an explosive. If you filled the entire pager, that would be even more room, but much more easily detected.

ethbr1 3 days ago

> I bet you could use a CR1216 battery (1.6mm thin, 30mAh, instead if 34mm long and 1500mAh) instead and have quite a good deal of spare volume in the battery for an explosive.

I'd be fascinated if that was the physical vector...

However, tainting a component pre-integration seems a lot more likely than simply packing explosive in the case.

Israel inserts the compromised components upstream in the supply chain, they're duly assembled into pagers, which then make their way to Hezbollah, where they're inspected, look normal, and work normally, and are then distributed.

That would still require a firmware hack to presumably trigger though (incoming message stack to component trigger).

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lxgr 3 days ago

> The electronics could be the size of the smallest wristwatch

Swatch actually used to sell a wristwatch that includes a pager! Battery life was pretty bad though; it came with a keychain accessoire to store a spare CR2032 and a battery swapping tool.

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formerly_proven 3 days ago

According to the manufacturer the pagers have a nominal battery life of about three months so it's not likely someone would actually notice if this number is cut in half or less.

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numpad0 3 days ago

Those thin coin cells can't output enough currents to replace most use cases. I've once tried to run ESP32 with couple CR2032, the ESP just browns out.

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LeifCarrotson a day ago
An ESP32 is a power hog meant to be plugged into a wall. Here are the current requirements for the various modes according to [1]:
Active mode, 260mA to 790 mA (!) Modem sleep, 20mA Light sleep: 0.8 mA Deep sleep: 10 uA Hibernate: 2.5 uA
Even with fancy DTIM beacons, Wifi and Bluetooth IoT devices just have a really power-hungry protocol stack and radio system to run.
Compare that to something like an STM32U5 microcontroller [2]:
3.1 mA Run mode at 160 MHz 19.5 μA/MHz Run mode at 3.3 V 6.6 µA stop 2 mode with full SRAM 1.7 μA stop 3 mode with 16 Kbyte SRAM 0.5 uA standby mode with RTC 0.3 uA standby mode (24 wakeup pins) 0.1 uA shutdown mode (24 wakeup pins)
And probably more importantly, an actual low-power microcontroller can wake from sleep in something like 4 microseconds, do something for a few cycles, and go back to sleep. Pager protocols are designed for this, putting the pager to sleep for sometimes an hour, and the crystal oscillator restarts the battery-powered device moments before the frame arrives, then goes back to sleep. Conversely, booting up the whole protocol stack on the ESP32 and acquiring a connection can take literally 4 seconds.
That results in a power consumption ratio on the order of 100,000,000. ESP32s are not efficient.
[1]: https://lastminuteengineers.com/esp32-sleep-modes-power-cons...
[2]: https://www.st.com/en/microcontrollers-microprocessors/stm32...
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