I had heard a rumor that automatic dialers were illegal but never checked it out, and this story made me think to do it.
It doesn't seem like they're illegal, but there's this, which was from 2004:
$1:
Predictive Dialing Devices
Some telemarketing organizations use automatic dialers to place telephone calls or send faxes. If a telemarketing agent is not available when the call is answered, then a "dead air" or hang-up call is the result. The CRTC's new rules say that
# telemarketers who use Predictive Dialing Devices must not abandon more than five percent of their calls per month, and must keep records of evidence to show that they have complied with this rule.
source Now, I always hang up whenever I don't hear someone on the other end immediately, because I know it'll be one of those dialers. Knowing that I'm screwing up their 'hang up call' percentage is good enough reason to not just ignore those calls from unfamiliar numbers
