This is a Habotest HT5910 RCD/Loop Tester, a digital professional tool for verifying the safety of residual current devices.
The device features a 4.7-inch LCD display for clear readings of voltage, resistance, and RCD testing parameters.
It measures tripping time and current for leakage switches with a testing voltage range of 0~440V.
The tester is rated for CAT III 1000V and CAT IV 600V safety levels, suitable for electrical installation maintenance.