Abstract 1,054,242. Correlation techniques. SEISMOGRAPH SERVICE (ENGLAND) Ltd. Nov.8, 1962, No.35266/66. Divided out of 1, 054, 241. Heading G1U. An apparatus for the filtering or transmission of a waveform comprises a first correlator for effecting cross correlation of the waveform against a reference waveform and a second correlator for cross correlating the output of the first correlator with a time inverted version of the same reference waveform. The correlators described in Specification 1, 054, 241 may be used for carrying out the required correlations. The present double correlating arrangement may be employed to improve the filtering technique described therein. To ensure that the output derived by the filtering correlator explained therein from a non periodic filter is directly significant it is fed to a recording head in a second correlator with a correlating head of the same form as that used in the first correlator, but reversed in time. This second head may also have shorting links and resistors so that two frequency selective actions are cascaded, the entire filtering action being achieved with zero phase distortion. Two such correlating heads may be incorporated in a single disc arrangement. Fig. 7 (not shown). The double correlating arrangement may also be used for the transmission and resynthesis of speech by coded phonemes, the derivation of which is discussed in Specification 1, 054, 241. The coded phonemes can be transmitted by signals of narrow bandwidth over submarine cables or satellite communication links and can be restored to normal speech by means of a correlator including reference heads which are the time inverse of the heads which produce the coded phonemes. These heads are used as recording heads to which the coded pulses corresponding to phonemes are applied. The recording heads lay down on the recording drum or disc a pattern which develops in a conventional play back head a voltage whose time variation duplicates the original speech.
APPARATUS FOR CORRELATING FIRST AND SECOND VARIABLES THE FIRST OF WHICH IS REPRESENTED BY VARIATIONS IN AN ELECTRICAL SIGNAL, WHEREIN THE APPARATUS COMPRISES A PLURALITY OF RECORDING HEADS, AT LEAST ONE PLAYBACK HEAD ASSOCIATED WITH EACH RECORDING HEAD TO FORM A PAIR, ONE OF SAID HEADS OF EACH PAIR INCLUDING A PLURALITY OF CONDUCTING ELEMENTS WHICH ARE DISTRIBUTED ALONG APART OF AN ENCLOSED CIRCULAR PATH AND REPRESENT A FUNCTION OF THE SECOND VARIABLE MEANS FOR PASSING A RECORDING MEDIUM AROUND THE SAID ENCLOSED CIRCULAR PATH SUCH THAT VARIATIONS IN THE SAID SIGNAL WHICH IS SUPPLIED TO THE RECORDING HEAD PRODUCE AN OUTPUT FROM THE ASSOCIATED PLAYBACK HEAD WHICH REPRESENTS A CORRELATION OF THE SAID VARIABLES, ERASE MEANS PROVIDED BETWEEN THE RESPECTIVE HEADS OF EACH PAIR FOR ERASING SIGNALS PREVIOUSLY RECORDED ON THE MEDIUM BEFORE THE LATTER REACHES THE RECORDING HEAD, THE RESPECTIVE RECORDING AND PLAYBACK HEAD BEING ARRANGED TO RECORD ON AND TO PLAY BACK FROM PARALLEL TRACKS ON THE RECORDING MEDIUM, THE HEADS BEING SO ARRANGED AND CONNECTED THAT WHEN THE SIGNAL REPRESENTING THE FIRST VARIABLE IS FED TO A FIRST RECORDING HEAD THE CORRELATED OUTPUT WHICH IS OBTAINED FROM THE FIRST PLAYBACK HEAD IS FED TO A SECOND RECORDING HEAD AND IS THEN CORRELATED WITH THE SAME SECONE VARIABLE BUT WITH THE LATTER REVERSED IN TIME.
Claim 2
Dependent Claim
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APPARATUS FOR CORRELATING FIRST AND SECOND VARIABLES THE FIRST OF WHICH IS REPRESENTED BY VARIATIONS IN AN ELECTRICAL SIGNAL, WHEREIN THE APPARATUS COMPRISES A PLURALITY OF RECORDING HEADS, AT LEAST ONE PLAYBACK HEAD ASSOCIATED WITH EACH RECORDING HEAD TO FORM A PAIR, ONE OF SAID HEADS OF EACH PAIR INCLUDING A PLURALITY OF CONDUCTING ELEMENTS WHICH ARE DISTRIBUTED ALONG APART OF AN ENCLOSED CIRCULAR PATH AND REPRESENT A FUNCTION OF THE SECOND VARIABLE MEANS FOR PASSING A RECORDING MEDIUM AROUND THE SAID ENCLOSED CIRCULAR PATH SUCH THAT VARIATIONS IN THE SAID SIGNAL WHICH IS SUPPLIED TO THE RECORDING HEAD PRODUCE AN OUTPUT FROM THE ASSOCIATED PLAYBACK HEAD WHICH REPRESENTS A CORRELATION OF THE SAID VARIABLES, ERASE MEANS PROVIDED BETWEEN THE RESPECTIVE HEADS OF EACH PAIR FOR ERASING SIGNALS PREVIOUSLY RECORDED ON THE MEDIUM BEFORE THE LATTER REACHES THE RECORDING HEAD, THE RESPECTIVE RECORDING AND PLAYBACK HEAD BEING ARRANGED TO RECORD ON AND TO PLAY BACK FROM PARALLEL TRACKS ON THE RECORDING MEDIUM, THE HEADS BEING SO ARRANGED AND CONNECTED THAT WHEN THE SIGNAL REPRESENTING THE FIRST VARIABLE IS FED TO A FIRST RECORDING HEAD THE CORRELATED OUTPUT WHICH IS OBTAINED FROM THE FIRST PLAYBACK HEAD IS FED TO A SECOND RECORDING HEAD AND IS THEN CORRELATED WITH THE SAME SECONE VARIABLE BUT WITH THE LATTER REVERSED IN TIME.