IU 400 Is an interface/analyzer for glass break detector GD 475 and shock detector CD 475. It has three relays one for Intrusion, one for Fault and one for Tamper. Max 10 units of GD 475/CD 475 detectors can be connected to one IU 400 unit.IU 400 together with GD 475/CD 475 is certified according to EN 50131-1 and EN 50131-2-7-2;2013 Grade 3, Class II. The IU 400 measures the current in a balanced alarm loop without end of line resistance, simplifying the installation. No need to keep track of the end of the loop. The detectors make up a balance under the control of the IU 400 processor. An end of line resistor of 2.2kohm is only required if the number of detectors is 3 or less. Changing the current in the loop of /- 0.8 mA for at least 200 ms. opens the IU 400 alarm relay for 2-3 seconds in (AUT mode) or stays open (Latch mode) until reset depending on how it is programmed. The loop in IU 400 operates in the current range of 3 mA to 30 mA corresponding to about 260 ohms to about 2600 ohms. Outside this area the LED will flash, and alarm- and fault relays are open and the device cannot be reset or programmed.