Before the cell phone there was the pager. You can't make phone calls with these small devices, but they enable communication and cannot be tracked.
The average consumer is most likely to see a pager in an old episode of the series “ER”. The small devices were something like a precursor to the cell phone. The basic idea: If you want to talk to someone, you ping the person's pager. The person sees the phone number – or a short message – and can call back or act on the message.
Pagers have been widely used since the 1980s, including by emergency services. However, the constant availability of mobile phones has made them largely redundant. However, the fire service, for example, still uses them to some extent. There are now also models of pagers that allow you to send a message back.
There is probably a simple reason why a militia like Hezbollah uses pagers on a large scale: unlike with cell phones or smartphones, their location cannot be determined. A normal pager is just a receiver that is not logged into a network. Activating all pagers in an area at the same time is no problem.
