The hot technology for alarm communication which never took off

The Derived Channel dialer in the 1980's along with Cable TV dialer where going to be the hot new technology's to take over for the old fashioned Direct lease phone lines that many community's had hailed as the savior of high phone fees and fast and convenient way to put many alarms on standard phone lines instead of tying up valuable copper pairs. That was till the big AT&T break up and the cheap and simple digital dialer with 2 phone lines for fire alarms came along and took the market by storm . With derived Channel as local telcos found out it was expensive to maintain the constantly supervised signal which required good solid clean phone lines something which was just not available in many big city's so Derived channel was all but abandoned and never had the big roll out that was anticipated only a handful of derived channel systems are even being used any more.
the city of Pittsburgh shut off its system over 10 years ago for fire alarm systems .Which ran thru Bell Atlantic.
Ademco and Radionics offered Derived channel dialer's for couple years and then stopped making them all together One of the unforunate failings of these units is they only took dry contact clousre or voltage triggers which greatly limited amount of info which could be sent unlike a digital communicator which could send individual zone info

At the same time Derived Channel came on the market Cable TV was making a big splash and engineers figured out a way for alarm signals to be sent over cable TV lines the now abandoned Moose security Products line was among the early producers of these dialer boards but unfortunately as one mid-west city found out you only needed one repeater in the field to go bad and the entire monitoring network could go down.
over 35,000 alarms with no service for an entire weekend.
So once again the digital dialer came to the rescue and now they say its day is coming but do not be so sure it is not going to totally die any day soon as lone as theirs a 2500 type connection business will use them over paying for cellular or internet based units which cost more money for small business. who do not have IP based phone systems.