For those who are younger than about 30, a pager is a small portable mobile device (smaller than many smartphones but bulkier) that (at least these days) has a display capable of displaying either just numbers or a text message. They are usually receive only; the message often contains a telephone number to call or instructs the recipient to take some action or be aware of something important. They started being used in Europe around 1970s (originally they just made a noise like a bleep) -in December 1975 the British Post Office boffins who had just moved to Adastral Park near Ipswich (not too far away from me) perfected a standard protocol for sending pager messages over radio that engineers at Koninklijke Philips Telecommunicatie in NL were also working on. (until 1990s Philips made a lot of equipment for the Post Office and later British Telecom).
This protocol is often still called POCSAG (Post Office Standards Coding Advisory Group) and works well when there is a lot of other radio interference.
Pagers are still widely used in ICT and healthcare; staff are often forbidden from carrying their personal GSM phones in some areas and much IT and telecoms equipment is often in places below ground level where the mobile signal can be non existent. There are national networks on VHF frequencies, it is also possible to install your own site system on a UHF frequency provided you get a Communications Ministry license. Messages are not private; anyone with a radio scanner or USB receiver can download software to decode them (although for a site system they would need to be in range of the transmitter) – but the system is way more reliable than SMS or anything else (its often used to alert engineers of system problems or hackers with big corporate computer servers).
I am currently setting up an onsite system for a site at work (it worked out cheaper and less hassle than trying to get the DECT phones to display messges as we use a mixture of analogue and digital base stations as well as different types of handset). The transmitter is British made (just outside London; coincidentally not too far away from the pirate station I was on!) It was even delivered ahead of schedule; even the Ofcom license arrived by email as soon as I had paid the £75 (although they did send the first email to a different site where the finances are handled and filling in their app form took 3 tries as I had to check the exact grid reference with a GPS (the signal isn’t always strong and by the time I’d got the grid ref the form had timed out and I had to start all over again).
At some random time on Thursday evening I tested the transmitter. The license comes with a strong warning not to use the system to send “misleading messages” which is fair enough; I was running the full 2 watts allowed by the license to an antenna which is facing open countryside – the signal could easily go 5 km or more, and these frequencies are shared with other users. If I sent messages like “Pls call Ahmed on Ext 222” there might even be a dude called Ahmed with a similar pager (whose job it is to fix any telecoms/networking kit that is playing up) who gets this message which wouldn’t be fair on him.
I therefore sent something so random that no one else could get it mixed up with their own comms (even if it might confuse them) and references POCSAG being perfected by both UK and NL. The messages do have some relevance to where I was in the building, and each “miauw” tests what other characters can be sent. To connect remotely to the serial link on another PC I had to use an old netbook on a WLAN which doesn’t work well in less than ideal signal areas, and cheap ISP-supplied routers in neighbouring buildings were increasing the interference (which is why organisations are going back to using pagers in the first place…).
I wouldn’t be surprised if NSA would try and contact Agentschap Telecom and BNetzA first to get it “translated” and try to send them on a wild goose chase around Sizewell, in spite of this TX being 30km the other side of there and me telling Ofcom exactly where it is situated 😀
(QRT means that I am switching off the TX until next time it is required; it will eventually be sending more sensible messages at the lowest power that works well…)
