This is a Digital Loop Impedance Tester with PSC with Anti Trip Technology for passive RCDs, it also  has a lock down test button for hands free testing

The key features of the Kewtech KT42 are as follows:

►  Digital - Loop and PSC (Prospective Short Circuit current) tester
►  Non-Trip Loop test on passive RCDs
►  Instant reading
►  20,200 & 2000 Ohm Loop measurement ranges
►  PSC Measurement up to 20kA
►  Displays mains voltage before test
►  Lock doqn test button - for hands free testing
►  Protected against phase to phase connection
►  Instant correct wiring status check
►  Complies with BS7671 (Part P)
►  Does not require batteries
►  External earth probe for earth electrode testing

►  KAMP 13 Mains lead
►  ACC016E 3 wire distribution board test leads
►  ACCEP5 external earth probe
►  Test lead pouch
►  Carrying strap
►  Instruction Manual
►  Certificate of conformity

LOOP Test Ranges
►  Loop Impedance Ranges: 0-20 Ohm, 0-200 Ohm, 0-2000 Ohm
►  Loop Impedance Accuracy: ±(2% + 2dgt)
►  Lowest Resolution 0.01 Ohm

LOOP Testing
►  AC Test Current: 25A nominal
►  AC Test Period: 20ms
►  PSC Ranges: 0-200A, 0-2000A, 0-20kA
►  Opperating Voltage: 230V ± 10%, 50Hz
►  Insulation Resistance: 50M Ohm at 1000V ac between electrical circuit and housing case.
►  Withstand Voltage: 3000V ac maximum for one minute between electrical circuit and housing case.

General
►  Safety Standard: Designed to comply with the requirements of BS4743
►  Dimensions: 175 x 115 x 86mm
►  Weight: 610g