. The Bell System technical journal . uency band is limited to 6 times thefundamental, « = 1 to 6, and F„ adjusted so that the charactersLetters V, M, 0, T and Blank are transmitted perfectly. The transfer admittance will now be determined for this case. Theexpression for /(/) may be written for the characters just mentioned,and would have the value 1/2 at ojt = a, for letters, at cot = 2a forV, at co/ = 3a for M, etc. Accordingly there result six equations whichmay be simplified as follows: MEASUREMENT OF TELEGRAPH 185 Letters 6 Y > — Sin na =1 n T fi Yn y —-
. The Bell System technical journal . uency band is limited to 6 times thefundamental, « = 1 to 6, and F„ adjusted so that the charactersLetters V, M, 0, T and Blank are transmitted perfectly. The transfer admittance will now be determined for this case. Theexpression for /(/) may be written for the characters just mentioned,and would have the value 1/2 at ojt = a, for letters, at cot = 2a forV, at co/ = 3a for M, etc. Accordingly there result six equations whichmay be simplified as follows: MEASUREMENT OF TELEGRAPH 185 Letters 6 Y > — Sin na =1 n T fi Yn y —- sin 2wa1 w - ,1/ 6 J^ V —- sin 3wGT n .7l7r- 0 V —- sin 4waT « - .297r- T 6 Yn V — sin Sna1 - Blank Y — sin 6na - The values of F„ computed by solving these equations were plottedon Fig. 30 and a curve was drawn through them. It will be under-stood, that, on the scale of abscissae, F is the fundamental frequencyof the character and the coefficients of F are values of 2F 5F 6F 7F Fig. 3F 4F FREQUENCY 30—Transfer admittance characteristic for undistorted transmission usingfrequencies up to seven times the fundamental frequency of the character. By the methods employed in the previous paper ^ it can be shownthat, for signals employing the same permissible intervals betweentransitions, the solutions of equations similar to the above approachthe smooth curve as a limit as the period of repetition is lengthened. These equations may be used to prove that when the six simplecharacters are perfectly transmitted, all other teletypewriter signalsmay be transmitted on a repeated basis. For distortionless transmis-sion f(t) should equal 1/2 at each transition point, assuming that the 186 BELL SYSTEM TECHNICAL JOURNAL relay operates at this value of current. If the expression for /(/) is written for each of the conditions which may occur, and is found to equal 1/2 at the transition points, the proof is complete. For this
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