From the article:
"Pen registers" refers to outgoing calls; "Trap and trace" refers to incoming. The etymology of the terms comes from the old-fashioned way of spying on people.
Today's telephone networks have the ability to capture this information without any special equipment. And the government has expanded the concept to include other forms of communication such as email.
The legal standard for conducting this kind of non-content surveillance is less stringent than the rules for conducting a wiretap. To get a wiretap order, the government must convince a judge that it is essential to an investigation, but pen registers must merely be "relevant" to an investigation to obtain the approval of a judge.
Not much to say there.... mostly a LOT more people... mostly.
Below is the Internet growth....
... these statistics likely don't include cell phone location tracking by law enforcement. They also omit government access to emails stored by third party providers. And they entirely exclude the National Security Agency's warrantless wiretapping program under the FISA Amendment Act.
I would normally be much more sarcastic about this... but it's just amazing how far we have come since the political duopoly took control.
(visit the link for the full news article)