A European format for digital transmission. E1 supports signals at 2 Mbps (32 channels at 64Kbps, with 2 channels reserved for signaling and controlling), versus the T1, which carries signals at 1.544 Mbps (24 channels at 64Kbps).
System integration is the way of putting together all the smaller parts called „subsystems” into one big system and ensuring that everything functions successfully together as a system.