This is a 2 Bit Relay operated Subtractor is working on 2's Complement method. As we have used full and half adder in place of Subtractor so this circuit can easily be used for both addition and subtraction. Due to out of space we couldn't make the model for both addition and subtraction. Only subtraction of two inputs are showing here. Please wait for 10 to 15 seconds to stabilize all Relays and produce proper Answer.
It is difficult to make the model until you are getting circuit diagram. Yet giving some hints, that may help you. Here 1-3= -2 Decimal A=1 and Decimal B=3, as it is a 2 bit model so Binary A=(0 1) and Binary B=(1 1). First invert B, now B=(0 0). Add A with B. (0 1)+(0 0)=(0 1) No carry. If final carry is 0 then invert the add result and put a negative sign. So final Answer is -(1 0) or Decimal -2. If final carry is 1 then negative sign off and add 1 with the add result to get the final Answer. Example 3-2, (1 1)+(0 1)=1(0 0) As final carry is 1 so add 1 with (0 0) and get final Answer (0 1) or Decimal 1.
