Patent GB-666316-A (GB)
Title: Improvements in systems for nullifying the effects of mutilated signals in electrical telegraph systems
Inventor: DUUREN HENDRIK CORNELIS ANTHON
IPC: H03M5/00
Filed: 1947-12-31
Abstract: 666,316. Telegraph systems. STAATSBEDRIJF DER POSTERIJEN TELEGRAFIE EN TELEFONIE. Dec. 31, 1947 [Nov. 18, 1946], No. 34972/47. Class 40 (iii). In a telegraphic system, particularly a radio transmission system, using an equal-unit code with a constant ratio of marking and spacing elements and in which the reception of a mutilated or disturbed signal causes a signal to be sent to the transmitter station to effect the repetition of the disturbed signal and those signals transmitted before the warning signal has been received, the signals are transmitted from a tape which controls a set of transmitter relays R1 ... R5 which operate further relays ZA ... ZG arranged to convert a five-unit signal into a balanced constant-ratio signal and to control the charging of m (4, as shown) sets of condensers Ca, Cb, Cc, Cd in accordance with the signals to be transmitted so that m successive signals are stored on the condensers. The arrangement is such that when a signal is to be repeated, the m sets of condensers previously charged according to m preceding signals are thereupon connected successively to the transmitter relays R1 ... R5, the tape transmitter being arrested and the m signals stored on the condensers controlling the conversion relays to generate the corresponding equal-ratio signals which are retransmitted prior to the resumption of transmission of signals from the tape. The control of the relays ZA ... ZG by the signals stored on the condensers is arranged to recharge the sets of condensers according to the five-unit signals which have been repeated so that the signals are stored on the condensers in case a further retransmission is necessary due to mutilation of the repeated signals. During normal undisturbed transmission, a relay P is de-energized, and a relay F, energized over contact p and contact member 6, holds contact f closed so that the selective setting of contact members 1 ... 5 correspondingly controls relays R1 ... R5. The charging circuits for the five condensers of the sets Ca, Cb, Cc, Cd are determined by contacts r1 ... r5 of the relays R1 ... R5 and contacts a, b, c, d closed successively for the period of a signal by relays A, B, C, D energized in succession by contact members 15 ... 18 carried on a shaft which makes one revolution during the period allocated to four signals. If the transmission is disturbed a transmitter device at the receiving station sends a signal which operates the relay P effecting the release of the relay F and operating a relay G which at contact g connects the set of relays R1 ... R5 in succession so that the four signals prior to the received notification-operation of relay P-are converted by relays ZA ... ZG and transmitted. The relay P when energized is held operated for a period corresponding to one complete revolution of the shaft carrying the contact members 15 ... 18. If the repeated signals are correctly received, relay P releases at the end of a revolution, relay F is reoperated and transmission from the tape is resumed. Conversion of five-unit code to equal ratio seven-unit code. The relays ZA ... ZE are selectively operated in correspondence with the relays R1 ... R5. An additional relay ZF is operated if one or both of relays ZB, ZC is/are operated, and the operation of one or both of the relays ZD, ZE operates relay ZG. A further relay ZK (not shown), is operated provided the perforated tape is not broken or exhausted. The contacts of relays ZA ... ZG which are energized in accordance with the elements of a signal are so arranged that marking or spacing potentials are applied in succession by contacts 8 ... 14 to the grids of valves L1, L2 to render the valves conducting in response to a marking signal so that a frequency applied at K1 appears at the output K2 for the transmission of a marking element. A spacing potential is provided only in those cases in which the operated relay contacts do not connect the less negative potential from the points marked M7 to the cams. The circuits for converting the five-unit code combination representing the letter " f " are described in detail in connection with Fig. 3. The impulses representing f effect the operation of relays ZA, ZC, ZD, ZF, ZG and ZK is also in operated condition. Spacing potentials are applied from S7 to contact members 8, 9, 11, 12. At contact 10 marking potential is applied via resistance R8, contacts za3, zg1, zfl, zb (unoperated), Zc2, and marking potential is applied to contacts 13, 14 from source M7 resistance R8, contacts zal, zg1, zf1, za2 and resistances R17, R18 respectively. These circuits have been extracted from Fig. 1. Two additional control signals in the seven-unit code-and not derived from five-unit signals-are generated respectively by the operation of relay SA (not shown) and of relays SA, SB (not shown). In these cases relay E is de-energized at operated contacts sal, sb1 and contact e is opened. Relays ZA ... ZG are all in their unoperated condition, and the generation of the two corresponding seven-unit signals is outlined in connection with Fig. 4 (not shown).