Emergency Communication Network (often shortened to ECN) refers to a network used by the local authorities (such as the UEE) of a certain system to monitor and keep their areas of space secure of any criminal activity. The network is established using a number of Comm Array stations that typically orbit each planetary body or natural satellite. 
Being in monitored areas of space results in criminal activity being directly registered with the local authorities. The player can receive fines for infractions, or even receive a crimestat.
The zone between the covered areas of space is deemed unmonitored space and criminal activity in this area cannot be monitored, which prevents infractions to be registered with the authorities. Players will therefore not get fines or a crimestat when committing crimes.
Players can use these networks to their advantage, such as criminals illegally taking down a Comm Array to hide in that sector of space. At Security Post Kareah, players can use a Cryptokey to hack into the Advocacy criminal database to wipe their crimestat, which will reset their crime rating throughout the monitored ECN space.
The ECN network can also be used by ships that are in distress. They can call out a distress signal that will be received by anyone linked to the ECN system. Players can then answer these calls and help out ships in need of help.