Patent GB-911826-A (GB)
Title: Improvements in means for decoding signals telegraphed in a binary code, and for controlling teleprinters
IPC: H04L17/30
Filed: 1959-09-22
Abstract: 911,826. Printing-telegraph receivers. VIERLING, O. Sept. 22, 1959 [Sept. 30, 1958], No. 32191/59. Class 40 (3). A circuit arrangement for translating n-unit signal code combinations of signal elements into pulses at selective outlets connected to printing members of a teleprinter, comprises a counting chain connected to the input of the signals and such that each link is formed by two bi-stable devices one of which is changed over by a positive signal element the other by a negative element, impulse gates controlled by the links to permit successive signal elements to pass to successive links of the chain which are connected to branches or stages each having a multiple of the number of selective control or switching elements of the preceding stage, the elements of the successive stages being controlled by the code elements applied to the associated links of the counting chain to provide a controlling output at one of 2n outlets individually connected to the printing members. In the diagrammatic arrangement, Fig. 1 (not shown), a selective circuit is built up in the usual doubling arrangement, the successive code pulses or elements controlling via the counting chain 2, 4, 8, 16 and 32 different paths to a selected one of 32 outputs. In the modified diagrammatic arrangement, Fig. 2, the first two elements of the incoming signal at L are applied via links N1, N2 of the counting chain so that one of the paths P1 ... P4 is closed. The third and fourth signal elements close a corresponding one of four paths of each of the groups Q1 . . . Q4, Q5 ... Q8 ... Q13 ... Q16, the effective group being determined by the path P1 ... P4 which has been closed. The fifth signal element passes via the closed path of the group P1 ... P4, the closed path of the group Q1 . . .Q16 to one of the two-position devices U1 . . . U16 which in response to the nature of the fifth element closes a circuit from a battery B through one of the actuating members K1 . . . K32, the circuit being completed over a contact e which is closed when the fifth element is received, and held for a period sufficient to allow the printing operation to take place. The links N1 ... N5 of the counting chain and the controlled paths of P, Q are restored to normal by a circuit R brought into operation by the link N5. The contact e is opened so that the members U1 . . . U16 are restored to normal. Detailed circuit arrangement.-The transistorcontrolled circuit, Fig. 3, corresponding to the diagrammatic arrangement of Fig. 2, comprises four pairs of transistors T1, T2 ... T7, T8 associated with the first four elements of the signal and a diode rectifier D5 by which the fifth code element is passed through the operative transistors of the P and Q groups to a two-transistor circuit, such as U3, effecting the selection of the output device K5 or K6. In the normal or rest condition of the arrangement, on account of the indicated values s a, b, c, d, e of the voltages applied to the various terminals of the transistors and rectifiers, all the transistors T1 . . . T8 are in the non-conducting condition, the diode D1 is biased to pass the input signal and the diodes D2 ... D5 are in a blocking condition. If the first code element is negative, the transistor T1 is rendered conductive, and applies a positive potential to the upper terminals of potentiometer resistances W#1 associated with transistors P1, P2. When transistor T1 conducts, the diode D1 is changed to the blocking condition, and diode D2 is made conductive so that the second code element can be applied to transistors T3, T4. If this element should also be negative the transistor T3 is changed to the conductive condition effecting the blocking of diode D2, the opening of diode D3 and applying a positive potential to the lower terminals of potentiometer resistances Wp2 associated with transistors P1, P3. Consequently the voltage at the tapping point t connected to the transistor P1 is raised to the level at which the transistor acts as an amplifier. Similarly the third and fourth code elements assumed to be positive and negative respectively apply voltages to the terminals of potentiometer resistances Wq1 Wq2, so that the transistor Q3 is biased to its amplifying condition. Since one of the transistors T7, T8 is rendered conducting by the fourth code element, the diode D5 is changed to its conductive state and the fifth code element passes via the active and amplifying transistors P1, Q3 to a junction point j connected to two transistors T9, T10 biased so that in combination with the voltage provided when the transistor Q3 has been made conducting, the negative or positive fifth element when amplified respectively renders transistor T9 or T10 conducting so that the appropriate final output member K5 or K6, such as a printing magnet, is operated. The fifth element is also passed over a conductor o to a restoring circuit, Fig. 5 (not shown), comprising a monostable trigger circuit formed by two transistors, one of which is switched by a positive or negative fifth element to control a third transistor producing a strong negative pulse applied to the bases of the transistors T1 ... T8 to restore them to their normal non- conducting condition. In the case of a code with an even number of elements, e.g. six, the fifth and sixth elements would be employed to select one of a group of four transistors, similar to a group such as Q1 ... Q4, connected by the transistor Q1 . . . Q 16 which has been made conducting by the third and fourth code elements. In a minor modification, Fig. 5 (not shown), the fifth code element amplified at the output from a selected transistor, such as Q3, from the group Q1 . . . Q16 is applied in parallel to oppositely poled rectifiers respectively connected in series with the final output members, such as K5, K6.