Advanced Technical Civilization.  A civilization capable of communicating across the galaxy or even greater feats of technology.

Most SETI research is concerned with the detection of an attention-getting "beacon" or acquisition signal, not a wideband data channel.

Continuous Wave (CW) transmission is when there is an electromagnetic carrier wave present and the message signal, be it voice, video or data, is impressed upon the carrier by modulating its amplitude [..]

Optical SETI observations can be done during the day under a clear blue sky with large professional telescopes.  See also Symbiotic Optical SETI.

Communication engineers like to express large power ratios in logarithmic decibels (dB).  Every factor of 10 in magnitude is a ratio of 10 dB.  Thus, an antenna gain of 1015

This is decibels with respect to 1 watt of power.

This is decibels with respect to 1 mW of power.  +30 dBm = 0 dBW.

Electromagnetic waves diffract around the edges of opaque objects or on passing through or reflecting off a finite aperture, like a dish, lens or mirror.  Even if such a wave is perfectly collimated, [..]

The Effective Isotropic Radiated Power (EIRP) of a transmitter (uplink) is the power that the transmitter appears to have if the transmitter was an isotropic radiator, i.e., if it radiated equally in [..]

A measure of the increase in forward transmitter power of an antenna or telescope with respect to that of an isotropic radiator.  An antenna is said to have a "directivity" since it [..]