Patent GB-654080-A (GB)
Title: Type-printing telegraph apparatus
IPC: H04L25/49
Filed: 1947-10-15
Abstract: 654,080. Type-printing telegraphy. DYMKE, E. Oct. 15, 1947, No. 27629. Convention date, Oct. 16, 1946. [Class 40 (iii)] In a keyboard-operated type printing machine each character is transmitted as a series of elements, each element consisting of either a series of positive impulses, a series of negative impulses, a series of alternate positive and negative impulses or a no-current impulse. A three-unit code is employed, the units consisting of positive half-cycles of an alternating current, negative half-cycles, both, or neither. Since the current of the first code element is used to start the receiver the no-current condition cannot be used as the first element. The number of combinations thus obtainable is 3 x 16=48. Transmission. The depression of a character key moves the required combination of code bars (Fig. 3, not shown) to close corresponding contacts u1 ... u6 (Fig. 2) which are arranged in pairs. When any key is depressed a seventh bar closes a corresponding contact u7 to connect to line the secondary of a transformer Tr to the primary of which is connected an A.C. source. When either or both of contacts u1, u2 are closed by the depression of a character key, positive or negative or both half-cycles respectively of the A.C. source are connected over the transformer secondary, contact u7, and contact f2 normally made, to a start relay KA which allows a cam-shaft A to be driven by a motor B via a one-revolution friction clutch. Cams F, G and H close in turn contacts f2, g2 and h2 for a third of a revolution, each to send to line in succession three signals. The signal sent by f2 consists of positive, negative or both half-cycles of A.C. derived from the secondary of a transformer Tr, the particular signal sent being determined by the setting of contacts u1 and u2 in conjunction with rectifiers Z1 and Z2. Contacts g2 and h2 similarly transmit the condition determined by u3 ... u6 and can send in addition a no-current condition since the second and third elements are not required to operate the start relay KA. The signals sent to line then selectively operate both the local receive relays E1, E2 and the distant receive relays C1, C2. Reception. At the receiver a type drum Y (Fig. 2) is divided into three sectors I ... III, in each of which are located sixteen type faces. The type drum has three homing positions indicated by the notches 1, 17 and 33 on the cam-face diagram of Fig. 2 and after printing the drum rotates to the next homing position. The reception of the first code element, which always contains at least one current condition, operates the start magnet KA and also the receive relays E1, E2 whose contacts e1, e2 register the signal on polarized storage relays R1 and R2 over the normally closed cam contact f1. The relay contacts r1 r2 in association with cam contacts ml ... o2 selectively prepare possible operating circuits for the receiver clutch magnet R7 according to the type-drum sector in which the desired character is located. The next received element is stored on relays R3, R4 since the cam contact f1 is now open and contact g1 is closed. Similarly, the third element is stored on relays R5, R6. Contacts g3 and h3 close in succession and each operates the clutch magnet R7 if a circuit is provided by the cam contacts m1 ... o2 in association with the storage relay contacts r1, r2. The type-drum Y is thus brought to the commencement of the correct sector and when the transmitter cam I closes its contact i the drum commences to rotate together with cams Q, R, S, T. The contacts q, r, s, t of the latter provide in conjunction with storage relay contacts r3 ... r6 a circuit path to operate the printing magnet V in one unique position of the chosen type sector. Since the transmitter shaft A is now latched at rest, the cam K completes the printing magnet circuit at k and the printing hammer strikes the recording paper against the required type-face. The type-drum continues its rotation until it reaches the notch at the end of the sector.