Patent GB-778843-A (GB)
Title: Type printing telegraph system
Inventor: DUUREN HENDRIK CORNELIS ANTHON
IPC: H04L27/10
Filed: 1951-09-04
Abstract: 778,843. Printing - telegraph systems. STAATSBEDRIJF DER POSTERIJEN TELEGRAFIE EN TELEFONIE. Sept. 4, 1951, No. 20874/51. Class 40 (3). A telegraph system in which signals are transmitted in a code in which all signal elements are of constant duration comprises two stations, each having a transmitter for transmitting traffic signals and service signals as well as a receiver device adapted to receive traffic signals and service signals, and operates in such a way that when a receiving device at a station receives a mutilated signal the associated transmitter transmits a service signal to request repetition and the printer at that station is blocked whilst the reception of the service signal at the other station operates its transmitter to repeat a number of signals including the mutilated signal whilst the printer at this latter station remains operative. When the system comprises more than two stations, the stations are regarded as constituting a ring operating in such manner that a station receives message traffic from the preceding station and transmits message traffic to the next station, its receiver device being adapted to react to service signals from the next station and its transmitter being adapted to transmit service signals to the preceding station in the case of mutilation. If, for example, there are three stations A<SP>1</SP>, B<SP>1</SP> and C<SP>1</SP>, A<SP>1</SP> transmits messages to B<SP>1</SP> and service signals to C<SP>1</SP>, B<SP>1</SP> transmits messages to C<SP>1</SP> and service signals to A<SP>1</SP>, whilst Cl transmits messages to A<SP>1</SP> and service signals to B<SP>1</SP>. The marking and spacing signal elements transmitted as frequencies above and below a predetermined frequency are passed from receiving terminals 1, 2 and transformer T1 to a valve B4 having in its output circuit tuned resonating circuits C2a, L2a and C2b, L2b connected to the valves B2a, B2b forming with valves B1a B1b a bridge and such that marking and spacing elements provide positive and negative voltages respectively at the cathode of the valve B1b. Disturbed signals or the unmodulated frequency produce zero voltage at the cathode of the valve B1b. The voltages corresponding to the marking and spacing elements are passed to capacitors I ... V by the contacts of a chain of distributer relays A ... D operated by contact e of a relay E in the anode circuits of a multivibrator MuRe operating at a frequency of 50 c.p.s. and synchronized with a multivibrator MuTr at the transmitting station by the transmission of a rest signal with solely a positive start pulse and passing the received pulse via contacts f, c2, a2 and connection CON to the grid of the valve B3a of the multivibrator. The contact f is operated simultaneously with the contact e by a relay F in series with relay E in the anode circuits of the valves B3a, B3b. The signal elements are sampled by further contacts of the relays A, B, C, D and when signal elements are received correctly one or the other of relays L, M is operated to break the circuit of a fault-indicating relay K. If an element is disturbed, relay K is operated and energizes a relay R which at contact r operates a counting chain N, O, P, Q effective to pass a positive pulse to a connection AC leading to the transmitter at the station which received the mutilated traffic signal. This pulse causes the transmitter to transmit a signal having a positive eighth element, which occurs in the seventh position of the element sequence, to the receiver at the station transmitting traffic and has the effect of producing a positive voltage at BC controlling the transmitter to effect a repetition cycle in which a signal comprising the basic frequency is followered by the retransmission of three signals stored on capacitors C1 ... C15, Fig. 1. The receiver at a station is selected by sending a combination of three elements such as the 1st, 3rd, 5th providing an output at terminals 6, 7 operating a relay S which at contact s charges a capacitor C17. After a number of operations of relay S a relay T is energized and operates a relay U which at contact u1 unblocks the printer, at contact u3 prepares a circuit for the warning signal and at u4 prepares a circuit for operation of the counting chain N, O, P, Q if mutilation of a signal occurs. Transmitting arrangements. Signals on a perforated tape are passed by selectivelyoperated contacts ke1 ... ke5 and closed contacts jt1 ... jt5 to capacitors C1 ... C15, the successive signals being distributed by contacts controlled by relays Kt, Lt, Mt, Nt and the elements being transmitted in sequence by the contacts of a chain of relays At, Bt, Ct, Dt, operated by a contact et of a relay Et in the anode circuits of the multivibrator MuTr and the contact ft of a relay Ft in series with the relay Et. The voltages are applied to the grids of valves B6a, B6b of a frequency-shift generator FSG producing variations above and below a standard frequency for the mark and space elements. The voltages applied over contact ft also operate a relay Gt which at contact gt passes back to the appropriate capacitor C1 ... C15 a charging voltage corresponding to the element transmitted, so that at any time three complete signals are stored. The tape is stepped forward by a magnet Hk operated when contact pt1 is closed by the energization of relay Pt which at operated contact pt2 permits the selective energization of the capacitor C1 ... C15. The circuit of relay Pt includes contacts qA, qB, qc controlled by the tape transmitter. The relay chain Kt ... Nt is started by the contact it of a relay It energized after the five elements have been transmitted. When a station is receiving messages, the transmitter at that station is set into operation to select the receiver at the messagetransmitting station and transmits the idle signal to bring the multivibrator MuRe at that station into synchronism. When a mutilated signal is received at the message-receiving station, the positive pulse on AC is transmitted during the seventh element period by contacts bt4, dt4 (operated) and ft (operated). At the receiver of the message-transmitting station this positive impulse is passed from capacitor S to the switch K1 connecting the receiver to the lead BC so that a pulse is applied to the message transmitter to inaugurate the signal repetition cycle. When the signal repetition is to take place, a counting chain Rt ... Ut is brought into operation by contact ut1 and relay Vt operated if the voltage on the conductor BC from the capacitor S of the associated receiver is positive or zero. At contacts rt4, st4, ut4 the circuit of relay Jt is interrupted so that contacts jt1 ... jt5 are opened and at contacts rt2, st2 and ut2 the circuit of the stepping magnet Hk is broken so that the tape transmitter is disabled for four signal periods. The contact wt will be in the position shown in the third and fifth element positions, and if during the warning signal period negative is on BC, Xt will be returned to normal and over contacts bt6, dt2 (operated) and xt relay It will be operated so that the chain Kt, Lt, Mt, Nt is set into operation. If, however, positive voltage had been encountered on BC, contact xt would not have been released and relay Vt would be operated so that the repetition counting chain Rt ... Ut is brought into operation and three more changes of contact vt are effective over contacts st3 and ut3 to cause the chain to control the transmission of a special signal and the three signals stored on the capacitors C1 ... C15. The first signal transmitted is the frequency without modulation and is produced by connecting ground via resistor R54, contacts tt2, rt3 (operated), bt5 (operated) to the grid of the valve B6a of the generator FSG. Specification 655,542 is referred to.