flop 44 is connected through the single pole of fourth relay 54 to the supply voltage v s the coil of this relay 54 is connected through current limiting resistor 56 to the low temperature signal output terminal 58 of the infrared monitor the output 60 of the flip flop 44 is connected through base resistor 62 to transistor 64 transistor 64 may be a pnp as shown in the figure if the base is connected to the inverting output of the flip flop 44 or an npn should the base of the transistor be connected to the noninverting output not shown of the flip flop an alarm reweld circuit 66 is connected between the supply voltage v s and the emitter 68 of transistor 64 and the collector 70 if transistor 64 is grounded through resistor 72 the alarm 66 may be an audible type alarm to alert the welder operator that a reweld is required alternatively the transister output generates a reweld signal which could trigger an automatic welder to weld again resistors 62 and 72 are selected to appropriately bias the transistor for the desired current gain and voltage necessary for the alarm circuit a description of the basic operation of the circuit now.