Consider the following statements as regards DPSK and DEPSK

1. DPSK demodulator requires a device which operates at carrier frequency and provides a delay of bit time T_b
2. In DPSK, synchronous demodulation recovers the signal b(t) and the decoding of b(t) to generate d(t) is done at base band
3. In both DPSK and DEPSK errors always occur in pairs

Which of the above statements are correct?