I check this forum most days, don't know how I missed this thread yesterday and earlier today. My apologies.
Richgolf, the Aritech CS-250 was marketed in both North America and UK & Ireland, that I know of. The answer to your question might depend on where you are.
IF you're in the USA, where I have most of my experience, the answer is that no municipal police department is equipped to receive signals from an alarm panel, not for the last 50+ years; not since before they stopped using stand-alone taped-voice dialers sometime in the 70s. The Aritech CS-250 is pretty old, but still recent enough that it has a communication format that requires a special receiver in a Central Monitoring Station (or "CS") to receive and interpret its signals, and CS personnel to call your local police department. In other words, you would need to contract with a Central Station to monitor your alarm system. Don't try to have it call your police station. If you did, they'd just get a series of calls (at least 8) and hear electronic beeps & twitters when they answer; and you'd probably get fined.
As I said, my experience is almost all in the USA---I go back to the days of voice dialers, in the 70s---but even then police depts were out of the alarm monitoring business. It might be different in some other country, but I'd be surprised.
@Martaine: Nice try, but your link is to the Owners Manual for the LCD Keypad, which is a different animal than the CS-250 Control Panel. What the OP needs is the Installation Manual for the CS-250 Control Panel---which, unfortunately I haven't been able to locate.