The DM-20 and CoreStation can detect 4 states such as ON, OFF, Open, and Short Circuit by using the Supervised Input port.
With the ‘Trigger and Action’ function from BioStar 2, you can preset the operation to perform when the DM-20 detects a state of Open or Short-Circuit.

Concept and Connection

The Supervised Input detects the voltage flow on the circuit and supervises the input device based on 4 states (Open, Short-Circuit, ON, OFF). The resistors need to be connected as below.

[Example of Supervised Input connection diagram] 


When connecting resistors as above, the circuit has the resistance as below.

  • When the switch is closed (ON), the current flows from the switch to R2 instead of R1 to R2. Therefore, the circuit’s resistance is 2.2 ㏀ (R2).

  • When the switch is open (OFF), the current flows from R1 to R2. Therefore, the circuit’s resistance is 4.4 ㏀ (R1 + R2).

  • When the circuit is open, the resistance is infinite and the current does not flow.

  • When the ground or the cable connected to the input port is shorted, the circuit’s resistance is 0.

[LED Status and Circuit Resistance of DM-20 based on the device’s state]

StateDM-20 LED StatusCircuit Resistance
ONGreen2.2 ㏀
OFFOff4.4 ㏀
OpenOrangeInfinite ㏀

[Reference Voltage]


  • You can use the following resistors for the Supervised input: 1 ㏀, 2.2 ㏀, 4.7 ㏀, 10 ㏀.
  • Do not use a resistor with different value (i.e 2㏀). 


Below is a sample configuration with CoreStation. 

Note the LED information based on the device manual. It is different from the DM-20.

1. In the DEVICE menu click on your CoreStation.

2. On Supervised Input, turn on the Supervised Input port you want to use. 

3. Select the Supervised Input Resistor value you have set up. 

4. On Trigger & Action click +Add.

5. For Supervised Input you have the normal option of Normally Open and Normally Closed but also Short and Open.

- Short and Open will appear as a Supervised Input event log when the event occurs

6. Click Apply and Apply again on the bottom of the page to apply the settings. 

7. On a short or open event below logs will appear in the event log. 

- port number is shown on the user column. 

More Information 

For diagrams regarding DM-20 refer to the DM-20 Wiring Example.

Regarding Corestation configuration and wiring diagrams, refer to How to Configure CoreStation.