101-001 (iTDC), 101-002 (EIO88), 101-145 (iTDCSR) -17- Users Manual
IDTeck – iTDC 2~4 DOOR ACCESS CONTROLLER
For the good grounding, we recommend to connecting ONLY one end of shield wire of communication
cable to grounding system; If you find earth ground nearby, then connect one end of shield wire to earth
ground; If you do not have earth ground nearby, then find chassis ground and connect one end of shield
wire to chassis ground; If you do not find both earth ground and chassis ground, then connect one end of
shield wire to power ground.
Note that if the chassis ground is not properly connected to the earth and floated from the ground level,
then grounding to the chassis ground will give communication problems; in this case we recommend to
use power ground instead of chassis ground.
Figure: Grounding system
4.2.4 REVERSE DIODE CONNECTION
If you connect an inductor (Door Locks or Alarm device) to the output relays, there will be a high surge
voltage created while the inductor is turning on and off. If you do not connect reverse diode, the surge
voltage will transfer and damage to the electronic circuit of the controller. It is strongly recommended to
add a reverse diode between the inductor coils to absorb this surge voltage.
Figure: Reverse Diode connection