Transmission device for the transmission of analog signals by means of pulse code modulation

Claim 2

A transmission device for the transmission of analog signals by means of pulse code modulation wherein for the purpose of generating the PCM signals the analog signals are applied through a duration modulating device to a counter controlled by clock pulses, characterized in that the pulse-duration modulating device is provided with two integrating networks having mutually greatly different time constants for pulse-duration modulation in accordance with four different slopes, each integrating network being connected to a counter controlled by clock pulses which counters provide the pulses of the greatest weight and of the smallest weight, respectively, of the code group characterized by the analog signal.

Claim 3

A transmission device as claimed in claim 1, wherein the integrating networks each include an integration capacitor, characterized in that the integration capacitor of the first integrating network is charged during a fixed period of time at a constant current which is proportional to the signal value to be converted, which integration capacitor is subsequently discharged at a constant current, the counting taking place during this discharge period in the counter controlled by the clock pulses and being connected to the first integrating network until the voltage of the integration capacitor has dropped below a comparison voltage of a comparator which causes the discharge of the integration capacitor to stop upon the next clock pulse and retains the occurring residual voltage, whereafter the integration capacitor of the second integrating network having a greatly different time constant is charged at a constant current which is proportional to this residual voltage during a fixed period of time and is subsequently discharged at a constant current, the counting being performed by the counter connected to said second integrating network until the voltage of this integration capacitor drops below a threshold voltage, while at the beginning of said second discharge also the capacitor of the first integrating network is completely discharged and remains discharged until the next signal value to be converted occurs.

Claim 4

A transmission device as claimed in claim 2, characterized in that upon exceeding its final state the counter connected to the second integrating network causes the counter connected to the first integrating network to advance by one step.

Claim 5

A transmission device as claimed in claim 1, wherein a compressor built up from logic circuits is incorporated in the transmission device.

Claim 6

A transmission device as claimed in claim 1, wherein the PCM-signals for recovering the analog signals are applied to a counter, characterized in that the transmission device includes two counters, the complement of the pulses having the greatest weight being written in in the first counter and the complement of the pulses having the smallest weight being written in in the second counter, clock pulses being applied to the first counter and a first reference voltage being applied to the input of an integrating network until after termination of the counting process in the first counter clock pulses are applied to the second counter and the input of the integrating network is switched to a second reference voltage which is a fraction of the first-mentioned reference voltage until the second counter has terminated its counting process, the analog signal being derived from the output signal of the integrating network with the aid of an output filter.

Claim 7

A transmission device as claimed in claim 5, wherein an expander built up from logic circuits is incorporated in the transmission device.