Patent GB-689140-A (GB)
Title: Improvements in or relating to multiplex pulse signalling systems
IPC: H04J3/00
Filed: 1951-02-16
Abstract: 689,140. Multiplex pulse signalling; valve gating circuits. SIEMENS & HALSKE AKT.- GES. Feb. 16, 1951 [Feb. 16, 1950], No. 3878/51. Classes 40 (v) and 40 (vi). [Also in Group XXXV] The phase-modulated interlaced channel pulses of a multiplex train are converted to amplitude-modulated pulses in a common circuit, the pulses then being fed to individual channel circuits controlled by appropriately phased gating pulses and a sinusoidal voltage the frequency of which is a subharmonic of the channel recurrence frequency to select the individual channel pulses for application to a storage condenser. In the embodiment described, the incoming twelve-channel multiplex train of phase-modulated pulses is applied, from terminal E, Fig. 1, to a synchronizing pulse separator B which controls the phase of a local pulse generator G. The latter produces two pulse trains from the output circuits T1, T2, whose recurrence frequency is half that of the pulses in the incoming train at E and which are phase displaced by 180 degrees. One train is applied to the gate circuits D1, D3, &c. for the six odd-numbered channels and the other to the gate circuits D2, D4, &c. for theevennumbered channels. A frequency divider F fed from circuit T1 provides a sinusoidal voltage of channel recurrence frequency to a phase shifter P which feeds twelve phasedisplaced sine waves to the gate circuits D1 ... D12 respectively. The incoming pulses at terminal E are also fed to all the gate circuits after conversion to amplitude-modulated pulses in circuit W, the locally-generated pulse trains from circuits T1, T2 being combined and fed to circuit W to effect the conversion. Each gate circuit passes its separated channel pulses to the channel outputs N1 ... N12 through amplifiers V. A phase control voltage for application to generator G is generated in the synchronizing separator circuit B by comparing the phase of the synchronizing pulses with that of rectangular waves, from the frequency divider F, which are of the same frequency as that of its sinusoidal output. Amplitude modulated pulses are derived from the phase modulated signal pulses (circuit W, Fig. 1) by applying them to the grid E1 of valve V1, Fig. 2, of a multivibrator V1, V2. The regularly occurring conversion pulses are applied to the anode of V1, from terminal E2. The multivibrator is thus alternately switched over by a pulse from each source and produces duration modulated pulses at the output terminal E3. These pulses block the rectifier Gl and allow condenser C to charge through resistance R2. At the end of each pulse, condenser C rapidly discharges, being shunted by resistance R1 and the conducting rectifier Gl. Amplitude modulated pulses thus appear at the output terminal A connected to the condenser. The gate circuit (D1 &c., Fig. 1) comprises a transformer U, Fig. 3, the ends of the divided secondary of which are connected through biased rectifiers Gl1, Gl2, to condenser CD and the output terminal K. The signal pulses from terminal J are fed to the mid-point of the secondary winding. The sinusoidal wave from terminals fx and, superposed thereupon, the selecting pulse train from terminals P1, are fed to the primary of transformer U through rectifier Cl3. When a selecting pulse coincides with a wave crest, rectifiers Gl1, Gl2, are rendered conducting to feed a signal pulse from terminal J to the condenser CD which stores the resulting charge until the arrival of the next pulse. The phase discriminating circuit (B, Fig. 1) comprises two biased opposed rectifiers Gl<SP>1</SP>, Gl<SP>11</SP>, Fig. 4, fed from the ends of the split secondary of transformer U<SP>11</SP>. The synchronizing pulse from terminal E is fed through valve Roll to the primary of transformer U<SP>11</SP> and the rectangular waves of channel recurrence frequency are fed to the mid-point of the secondary from terminal FB. The synchronizing pulses render the rectifiers Gl<SP>1</SP>, Gl<SP>11</SP>, conducting to feed part of the rectangular wave to condenser Ce and the output terminal M. This part is positive or negative depending on the relative phase of the inputs and a correcting voltage is thus developed across condenser Ce, for application to the generator producing the wave, until the synchronizing pulse coincides with the point of the wave at which a polarity change occurs, and from which zero correcting voltage is produced.