The 1040-4B serves as a voltage or current source for testing or high-potting telephones, intercoms or electrical appliances. The 250+ volt photoflash battery is applied to the OUTPUT LEVEL control.  The momentary ON/OFF switch serves as both a safety feature and battery saver.  The negative side of the supply, which is isolated from the case, is tied directly to the BLACK - terminal. The positive output is derived from the center contact of a 1 Megohm potentiometer and is current limited through a 47K resistor.  In operation, the RED + terminal may be varied from 0 to 250 volts DC (no load condition).  The voltage and current output of the 1040-4B are a direct function of the resistive load applied.

OPERATION:  Insert the BLACK test lead into the BLACK - jack.   Insert the positive (RED) lead of the multimeter into the RED + jack.  Set the multimeter on the six (6) milliamp (mA) range. The scale used on the Simpson 310 meter indicates 0-60 in black with 60 being 6 mA.  Short the BLACK lead from the multimeter to the BLACK test lead connected to the 1040-4B BLACK - jack. Hold the momentary ON switch UP for a few seconds and then set the OUTPUT LEVEL for a reading of one (1) mA or 10 on the 0-60 black scale.  Release the power switch and separate the BLACK test leads.  Now, whenever the switch is turned ON, approximately 250 volts DC will appear at the end of the two BLACK leads. BE CAREFUL!!! Set the meter on the .6 mA or 600 microamp (uA) range. The 0-60 black scale is now 0-.6 mA or 0-600 uA full scale. Shorting the black test leads together will cause the meter pointer to swing full scale.  This much over-range will not damage the meter. Using the two BLACK test leads proceed with normal hi- potting procedures to test telephone hook-switches, lamps, appliances, etc.  Any meter indication means a resistive path exists which should be checked.