To understand how to convert a signed binary number in two's complement representation from the binary system to decimal (base ten), the easiest way is to do it by an example - convert binary, 1101 1110, to base ten:

• In a signed binary two's complement, first bit (leftmost) indicates the sign, 1 = negative, 0 = positive. The first bit is 1, so our number is negative.
• Get the signed binary representation in one's complement, subtract 1 from the initial number:
  1101 1110 - 1 = 1101 1101
• Get the binary representation of the positive number, flip all the bits in the signed binary one's complement representation (reversing the digits) - replace the bits set on 1 with 0s and the bits on 0 with 1s:
  !(1101 1101) = 0010 0010
• Write bellow the positive binary number representation in base two, and above each bit that makes up the binary number write the corresponding power of 2 (numeral base) that its place value represents, starting with zero, from the right of the number (rightmost bit), walking to the left of the number, increasing each corresonding power of 2 by exactly one unit:

• powers of 2:	7	6	5	4	3	2	1	0
  digits:	0	0	1	0	0	0	1	0

• Build the representation of the positive number in base 10, by taking each digit of the binary number, multiplying it by the corresponding power of 2 and then adding all the terms up:
  

  0010 0010₍₂₎ =

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  (0 × 2⁷ + 0 × 2⁶ + 1 × 2⁵ + 0 × 2⁴ + 0 × 2³ + 0 × 2² + 1 × 2¹ + 0 × 2⁰)₍₁₀₎ =

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  (0 + 0 + 32 + 0 + 0 + 0 + 2 + 0)₍₁₀₎ =

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  (32 + 2)₍₁₀₎ =

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  34₍₁₀₎

• Signed binary number in two's complement representation, 1101 1110 = -34₍₁₀₎, a signed negative integer in base 10