Guarded Nanovolt Detector, model 9838, with 240 volt to 115 volt transformer, metal / plastic, made by Leeds & Northrup / Ferguson, North Wales, Pennsylvania, United States of America, 1965-1980, used by Telecom Laboratory Services, Strathfield, New South Wales, Australia, c. 1967-1990
The instrument is in a black metal case with a meter, three rotary knobs, two lights, and a two position switch on the front face. The centre point of the mirror-backed meter is marked '' with numbers from 1 to 5 to the right and left and graduations marked every 0.2 of a unit. The top rotary knob selects 'CHARGE', 'OFF', 'AC LINE', 'BATTERY', 'OFF', BATTERY TEST'. It is flanked by two small yellow and red plastic covered indicator lights. The left lower rotary knob is labelled 'SENSITIVITY' with numbers from 0-10. The two position switch is labelled 'OUT' 'IN'. The switch and the right rotary knob are labelled 'ZERO SUPPRESSION'.
The back of the detector has the power lead labelled '120V' '50-60 Hz', fuse and screw terminals, two labelled 'METER', two labelled 'REC + -' and two labelled 'BA - +' and a four wire lead labelled 'INPUT'.
The transformer is used to convert 240 volts to 115 volts to power the nanovolt detector. The power lead from the detector plugs into the back of the transformer.
The face of the unit is marked:
'LEEDS & NORTHRUP'
'9838 GUARDED NANOVOLT DETECTOR'
No serial number is visible on the unit.
Dymo labels on the back of the unit are marked:
The transformer is marked:
PRi. 240V. 50Hz.'
'SEC. 115v. .26A. 30V.A.'
'0.35A. FUSE OUTPUT END'