That might be similar, it has a dialer. The 521 does not.
That unit has the very same motion detector that the 521 doesn't seem to recognize.
The 521 recognized and installed all the door sensors and keypads/keyfobs the magnavox thing used.
But I haven't had success with the PIR yet.
It's not walk testing at the moment, so it might be just from age.
I had to scrap out a brand new door sensor, it installed but then a few hours later got flaky.
