| 摘要 |
A message signal (RFA, RFB) is transmitted from a transmitting unit (10) to at least one receiving unit (25) in a state coded by means of an encoder (13). Simultaneouly, a separate control signal (SD), generated by the transmitting unit (10), is transmitted and causes a decoder (28) in the receiving unit (25) to accomplish a coding operation on the received coded message signal (RFA', RFB'), timely coordinated with the coding operation. The control signal (SD) consists of a continous data stream, composed of frames (F) of equal length. Each frame (F) contains a predetermined frame synchronization word (FW) which defines a cyclically recurring reference time (Tref) for the transmitting unit (10) and which is utilized in receiving unit (25) to determine a corresponding cyclically recurring reference time (Tref') for this unit. At least some frames (F) also contain data which define the time (t2A, t2B) for an alteration of the operating mode of the encoder (13), related to said reference time (Tref) for the transmitting unit (10), and which are utilized in the receiving unit (25) to determine a time (t2A', t2B') for a corresponding alteration of the operating mode of the decoder (28), related to said reference time (Tref') for the receiving unit (25). |
