: : : How is a black hole detected and what is the device called that does the detection.

: : Detection is by a combination of two things. : : (1) No radiation directly...

: There is a lot of radiation we pick up from around the hole due to matter around the hole that hasn't yet crossed the outer event horizon.

What you say is correct, but you miss the point. Any object with a strong gravitational field would have an accretion disk under the same circumstances. What distinguishes a black hole is its lack of radiation. For example a nuetron star is quite often a pulsar, while a large shining star would outshine an accretion disk (e.g. binaries).