TESTO 6681 Instruction Manual page 31

Use of relay as NC contact (NC = normally closed)
Alarm/status light
(example of installation)
250 V AC/DC, 3 A
The busy light (alarm/status light) is permanently on until the
relay opens or the circuit is interrupted. This circuit can
therefore be used to monitor the functionality of the alarm
circuit, as a cable break, for instance, is indicated by the busy
light going off.
Use of relay as NO contact (NO = normally open)
Alarm/status light
(example of installation)
250 V AC/DC, 3 A
testo 6681 Ethernet
- 1.3 Commissioning 31