This instrument was designed specifically for testing telephone lines and equipment so some of its features are not needed for general purpose
testing. It has a 12 position switch which selects the various ranges. The first
position, although marked "off", is the AC voltage measuring position. Up to 250V AC can
be measured and the test probe should be connected to A+ and B- as for all other ranges
except the insulation test range 12. The reason why this position is marked
"off" is because in any other position of the switch the battery is in circuit and would be discharged unnecessarily, so always turn the switch fully
anti-clockwise.Positions 2 and 3 are special circuits for testing GPO equipment and batteries and are not for other use.
Position 4 is the high ohms range, with the probes touched together the pointer should indicate zero ohms. When measuring resistance then multiply the scale, reading by 100. A further use for this range is, for testing the goodness of capacitors. When the probes are connected across a capacitor and the push button is engaged, the meter movement will deflect on an amount depending upon the value of the capacitor. When the probes are first applied, the pointer will move over and fall back to zero if the capacitor is good. If it stays over, then there is a leak. If you care to, you could note the deflection with various capacitors which would give you some idea of the value of an unknown capacitor.
Position 5 is again an ohms range - use as for previous position but don’t multiply the scale reading by 100. This should be regarded as the low ohms range.
Position 6, 7 and 8 are for reading DC voltage up to 250V.
Positions 9, 10 and 11 are for reading DC current, 5A on range 9, 500mA on range 10 and 50mA on range 11. A useful thing to remember when using these current ranges is that should you have connected your instrument the wrong way round and you are getting a negative reading, then the push switch on the right-hand side reverses the connection of the meter and will give you a positive reading.
Position 12 is the insulation testing range. To use this range you must move the probes between B- and E. In this switch position the internal generator increases the voltage from 9 to approximately 150 so you are testing insulation at quite a high voltage. You will get a reading on the bottom scale up to 5M but a good insulation should show no reading, this is what is known as infinity.