2. The system according to claim 1 wherein said means responsive to said complex waveform for developing coded signals representative of said individual slopes comprise means responsive to said complex waveform for developing a signal representative of instantaneous slope of said complex waveform, and a coder means responsive to said signal representative of said instantaneous slope for producing individual coded signals representative of slopes of the complex waveform, each individual coded signal covering an individual range of adjacent slopes; and further including means responsive to said complex waveform for detecting when the slope of the complex waveform changes from one range to another, and a timing circuit means responsive to an output from said means for detecting when the slope of the complex waveform changes from one range to another for determining the duration of time for which the slope of the complex waveform lies within a range of slopes.

3. The system according to claim 1 wherein said means for developing coded signals representative of said individual slopes and said means for developing coded signals representative of said given durations are means for developing coded signals in binary form.

4. The system according to claim 2 wherein said means for developing a signal representative of instantaneous slope of said complex waveform comprises a differentiating circuit means, and said coder means comprises an analogue-to-digital converter having an output in binary form.

5. The system according to claim 4 wherein said means for detecting when the slope of the complex waveform changes from one range to another comprises means responsive to said output in binary form for detecting change in the output of the analogue-to-digital converter.

6. The system according to claim 5 wherein said timing circuit means comprises a source of clock pulses, a digital counter coupled to said source of clock pulses and responsive to clock pulses therefrom, said digital counter being coupled to said means for detecting when the slope of the complex waveform changes from one range to another for receiving a re-set signal therefrom.

7. The system according to claim 6 including means responsive to said compelx waveform for determining if the instantaneous slope of said complex waveform is below a predetermined value; means responsive to count output from said digital counter for determining if the count of the digital counter is above a predetermined value; and means responsive concurrently to an output from the means for determining if the instantaneous slope is below a predetermined value and an output from said means for determining if the count of the digital counter is above a predetermined value for apportioning bits of at least one word between at least one of said coded signals representative of at least one of said given durations and at least one of said coded signals representative of at least one of said individual slopes, and for producing and inserting a signal in said at least one word to indicate apportionment of bits of said at least one word to slope information and duration infOrmation.

8. The system according to claim 1 wherein said means for producing an analogue signal corresponding to said complex waveform comprises decoding means responsive to said coded signals for producing one signal representative of the individual slopes of the complex waveform and another signal representative of the given durations, an integrating means, and switch means responsive to said another signal for selectively feeding said one signal to said integrating means for time durations equal to the given durations.

9. The system according to claim 8 wherein said means for transmitting said coded signals includes means for producing a series of signal words, each word containing a signal representative of an individual slope and a signal representative of a given duration; said decoding means comprises an input register for storing incoming signal words, a word splitting means coupeld to said input register for splitting stored signal words received therefrom into their slope representative portion and duration representative portion, a first digital-to-analogue converter means responsive to the slope representative portion of said stored signal words for producing an analogue slope representative signal, a second digital-to-analogue converter means responsive to the duration representative portion of said stored signal words for producing an analogue duration representative signal, and a converter means responsive to said duration representative signal for producing output pulse signals each pulse of which has a duration equal to one of said given durations, said switch means being controlled by said output pulse signals.