Patent GB-461753-A (GB)
Title: Tell-tale device for telegraph printing apparatus
IPC: H04L12/06
Filed: 1935-08-27
Abstract: 461,753. Telegraph exchange systems. GRIFFITH, R. G. Aug. 27, 1935, No. 23949. [Class 40 (iii)] An automatic telegraph transmitter, for use as an answer-back device, comprises a code drum or other unit such as an endless band having projections, perforations &c. representing a series of predetermined permutations to be set up on a set of selector or contact controlling members, the drum being yieldingly driven and arranged to be arrested and released between each successive permutation setting operation. The selector or contact controlling members are also set by a keyboard for message transmission. Keyboard transmitter. The keyboard 1 and arrangements for tripping the overlap camshafts 12, 30, 43 controlling transfer and selector mechanism are generally similar to the arrangements described in Specifications 447,196 and 448,846 except that the first cam-shaft 12 moves a quarter revolution instead of a half revolution each time it is tripped, and the keyboard sets up 5-element permutations instead of six. Each time shaft 12 is tripped, it rocks a frame 14 to position a set of transfer members 17 and forked levers 24 in accordance with the setting of members 19 by the keyboard, the transfer members 17 and levers 24 being similar to corresponding arrangements described in Specification 439,745. The setting of the levers 24 is transferred to a further set of transfer levers 32 by the second overlap shaft 30 which is released after a convenient angular movement of the first shaft 12. The lower ends of the levers 32 are slotted at 34 to engage a pivot bar 35, and if a forked lever 24 is in the position shown, the corresponding transfer lever 32 is moved counter-clockwise by cam-shaft 30. If, however, a lever 24 has been moved counterclockwise, a stop 36 thereon frees the lower end of its transfer lever 32 which is swung idly by the cam-shaft. The effectively operated levers 32 rotate corresponding levers 28 in a clockwise direction to release latch members 40 and the third overlap cam-shaft 43 is released after a suitable interval. The latch members 40 each control a pair of levers 45, 46 in a similar manner to the levers 24 and transfer members 32, so that with a latch member in the position shown, cam 44 rotates lever 46 counter-clockwise to move a selector bar 47 to the left while lever 45 swings idly, whereas if the latch member has been released to move counter-clockwise, lever 45 moves bar 47 to the left while 46 swings idly. When the transfer has been completed, the released latch members are restored by cams (not shown) on shaft 43. Setting of selector bars by code drum. The " who are you " signal causes, in a manner not described, the clockwise movement of lever 61, Fig. 3, whereby a detent 68 is released from a notch 69 in the code drum 59 through the medium of levers 65, 66, the drum being yieldingly driven by a slipping clutch from the power shaft. The drum has a number of wards cut so as to engage tails 71 of levers 28 in different permutations, and is released and arrested between every permutation by an escapement 79, 89, but the first few wards 60a are dummies and are also notched to clear finger 79 of the escapement so that the drum has an initial continuous movement, until the first effective ward engages the finger, for the purpose of giving time to the transmission circuit to condition itself, and to lock the keyboard. The locking is effected by a lever 81 having a tail 83 which, on release of the drum, rides up notch 84 and depresses member 86 to hold an additional vane 8 whereby the frames 2, 2a are prevented from being depressed by the keys. When the first effective ward reaches finger 79, escapement arm 90 is moved clockwise and finger 89 stops the drum. Arm 90 operating on fork 74 releases cam-shaft 43 and the ward operates on levers 28, the setting of which is transferred to selector members 47 as previously described. Immediately afterwards, cam 73 operating on prong 75a of fork 75 releases the transmitting cam-shaft (not shown) through link 77, the fork 75 being restored by the transmitting shaft when the impulses have been sent. The shaft 43 is stopped by cam 73a and prong 75b if, in the meantime, fork 75 has not been restored. Subsequently, cam 72a engages prong 74b to restore fork 74 and prong 74a stops shaft 43, escapement arm 90 being operated to release the drum to bring the next ward into action. The wards can be changed by removing an end plate of the drum. Sending the " who are you signal and locking the code drum at the calling station. The signal is sent by a special key 1a, Fig. 3, and as it is necessary to lock the drum since the receiver at the calling station also responds to the signal, the selector frame 2a corresponding to key la has a projection 196 which operates on lever 97 to lock the detent 68 in the notch 69 of the drum. As levers 65, 66 are locked, lever arm 63 is attached to the lever 61, which responds to the signal, by a yielding connection.