The turbo-principle is more far reaching than the original turbo code concept. Encoded DPSK transmission, e.g., can be viewed as a serial concatenation of a channel code with a rate-one code representing the DPSK modulation. Iterative decoding of this concatenated scheme shows surprisingly good performance. We describe the serial concatenation of interleaved tail-biting convolutional codes (TBCC) with this DPSK rate-one code transmitted over AWGN and flat Rayleigh fading channels. The receiver performs time-continuous "turbo" iterations between the inner and outer codes and is realized by two analog ring networks connected via an interleaver ring which exchanges extrinsic information by means of analog signals being continuous in time and value.