ANLEGGNING FOR OVERFORING AV INFORMATIONSSIGNALER GENOM PULSKODMODULATION

1534339 Adaptive delta modulation PHILIPS ELECTRONIC AND ASSOCIATED INDUSTRIES LTD 11 Feb 1976 [14 Feb 1975] 05366/76 Heading H3H In an adaptive delta modulation p.c.m. transmitter the information signal is compared at 2 with a locally generated signal derived from a decoder 10, clocked ouput pulses are fed to the receiver and to a dynamic control unit 11 which controls the output of modulator 12. The modulator comprises a 1st current controlled current source 22 outputting to a difference amplifier 24, switched by the pulse train, which outputs to identical 2nd and 3rd current controlled current sources 30, 29 where outputs are respectively directly and through a polarity reversing circuit 37 to the decoder. The arrangement differs from that of Specification 1,440,996, in that the modulator is provided with 4th and 5th current sources 44, 45 and a 6th current controllable current source 50 which act to make the output current pI, equal to the dynamic control output by acting as a feedback loop. The arrangement is suitable for monolithic construction and the 2nd, 3rd and 6th sources are preferably identical and of PNP form while the 5th source is a current mirror of NPN form. The receiver is of similar construction, the dynamic controller being synchronized with the transmitter clock pulses. Reference has been directed by the Comptroller to Specifications 1,261,951 and 1,440,996.