THORLABS ITC4000 Series Operation Manual page 55

3 Operating the ITC4000 Series
I/O port source operation
In above circuit, the output drives an optocoupler in source operation. This component may be
replaced by a LED or a switching transistor. To switch the connected device to on-state, the
output level of the digital I/O line must be set HIGH. The maximum source current is 2 mA.
I/O port sink operation
In above schematic, the output drives a relay in sink operation. Note that the external relay coil
is connected between the digital I/O line (pins 1 ...4) and +12 V (pin 6).
To energize the external relay, the output level of the digital I/O line must be set LOW. The
maximum sink current is 400 mA.
If a lower supply voltage is required for the relay, a standard voltage regulator may be inserted
between pin 6 and the relay coil contact.
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