HDT/6/24-F* is a range of combined two-stage surge protection intended for a low voltage data and power supply lines routed by a common cable. An example might be a pair of RS485 data line wires and a pair of 24 V DC power line wires routed by a common cable from the control system to remote sensors requiring an external supply voltage. The module can also be used to connect many other types of analog or digital sensors with symmetrical or asymmetrical output. The protection module must be installed just before the protected device. The 1st stage of surge protection consists of three-pole gas discharge tubes, the 2nd stage is using transils. The overcurrent protection of the power supply line is ensured by a PPTC resettable fuse. The fuse heats up during the overcurrent and its internal resistance increases by several levels. This will limit (not interrupt) the flowing current. The green LED has only an orientation function about the presence of voltage on the power supply line. To reset the resettable fuse, the circuit must be switched off and let the fuse cool down. Unlike a standard fuse, resettable fuses do not have to be changed, which can reduce the service interventions or make the service faster.
* There is no need to replace the fuse and call a technician – all you have to do is repair the fault on the device behind the protection and then switch it on again