| 摘要 |
991, 994. Selective signalling. INTERNATIONAL BUSINESS MACHINES CORPORATION. May 22, 1963 [May 24, 1962], No. 20310/63. Heading G4H. [Also in Division H41 A pulse code modulation system for transmitting the excitation pulse spacing in a channel vocoder system (see Division H4) comprises Fig.7 a binary counter 11 which counts pulses from a source of quantizing pulses 14, the pulses being gated into the counter by a pulse from a source 15 whose pulse repetition frequency is equal to the lowest excitation frequency expected, e.g. 150 cps. The counter counts pulses from the source 15, at e.g. 15 kc/s, until an excitation pulse arrives to close gate 12. The resulting number stored in counter 11 is passed, on occurrence of the following pulse from source 15, into a shift register 17 so that the parallel stored binary number is serially transmitted over the line 20, the counter 11 being reset by the pulse from source 15 after a suitable delay provided by circuit 18. At the receiver a shift register 24 receives the P.C.M. signal and when the register is full the signal is transferred into the counter 27 to set the counter to the complement of the count in the counter in the transmitter. The counter 27 then counts the quantizing pulses from source 26 until the full count is reached when a pulse is generated which is passed for shaping to shaper 31 to form the excitation pulse for the receiver. |
