Patent GB-452528-A (GB)
Title: Improvements in coding and decoding apparatus
IPC: G09C3/00
Filed: 1935-05-17
Abstract: 452,528. Typewriters for ciphering. INTERNATIONAL BUSINESS MACHINES CORPORATION, 270, Broadway, New York, U.S.A.-(Assignees of Lemmon, W. S.) May 17, 1935, No. 14537. Convention date, June 16, 1934. [Class 146 (ii)] [See also Group XVI] A coding and decoding apparatus comprises a primary manually operable machine having a keyboard with character keys and a space bar and a secondary machine having character keys and a space bar, the two machines being interconnected so that operation of the primary machine causes the production on the secondary machine of a code message in which each letter and space of the uncoded message is replaced by a character and which is automatically divided up by spaces into equal groups, an electric switch or the like being provided whereby the operation of the apparatus may be changed instantaneously from coding to decoding to cause the writing of the coded message on the primary machine, including all the characters and spaces thereof, to produce in the secondary machine an exact reproduction of the uncoded message, with the original characters and spaces correctly included and the automatically introduced spaces eliminated. The apparatus consists of a primary typewriter 1 and a secondary typewriter 2, both of which are electrically operated, being driven by electric motors and each comprising a constantly rotating cylinder 3 which operates cams 4, 5 to actuate the carriage feed-mechanism or the type bars 6 when they are tripped by the space bar 7 or a character key 8. Depression of an ordinary key 8 results in the appropriate cam closing one of a number of switches 19 each of which is connected to a ring 36, all the rings being mounted on a common rotatable shaft 37 and insulated from one another. Each ring 36 is connected to a contact 39 all of which are arranged round a disc 40 and engage insulated segments 42 on a second disc 41. The disc 40 is fixed to the shaft 39 but the disc 41 is fixed to a stationary bracket so that when the shaft is rotated, the contacts 39 engage different segments 42. The segments 42 are connected to the solenoids 48 for operating the type levers of the second typewriter 2 so that depression of a character key of the typewriter 1 actuates a type lever of the typewriter 2 and the particular type lever actuated can be changed by altering the position of the disc 40 relatively to the disc 41. This code change can be effected by rotating the shaft 37 by a ratchet 119 fixed to the shaft and operated by an electromagnetically controlled pawl 120, the circuit of the electromagnet 155 being completed by a switch 143. This switch is closed by projections 142 on a disc rotated by a second rotary disc 139<a>, the arrangement being that the disc 139<a> is rotated by a finger inserted in one of the holes 140 until the finger reaches the stop 141 when the disc is released and in its backward movement drives the disc carrying the projections 142, the extent of the rotation and therefore the number of actuations of the switch 143 depending upon the extent to which the disc 139<a> is rotated. At each actuation of the switch 143 the ratchet 119 is rotated by the extent of one tooth so that the discs 40 and 41 may be brought to any desired relative position. The initial or zero position of the disc is indicated by a signal light 133 which is actuated by a projection 131 on the ratchet wheel and the discs may be brought rapidly to this position by a short-circuiting tapping key 159. To prevent unauthorized change of the code, the circuit of the electromagnet 155 includes a switch 148 which may be fixed open by a key-operated lock 158. The code may also be changed automatically at the end of each line by closing a key 164 operable by the carriage return key 164a. The typewriter 1 prints the message to be coded or uncoded while at the same time typewriter 2 prints the message in its coded or uncoded form according to the setting of a switch 174. The coded message is divided into groups of five letters irrespective of the lengths of the words when a switch 79 is closed, by means of a rotary contact maker 71 which is rotated by a pawl and ratchet at each key operation and completes the circuit of the space solenoid of the typewriter 2 at every fifth letter whereby the space bar of this typewriter is actuated. In coding, the switch 174 is thrown over to the left and this connects the switch 19
 of the space bar of typewriter 1 to a segment 42 of the disc 41 so that when the space bar is operated a letter such as " B " is printed. The " dash " key (or some other little-used key) is however disconnected in this position of the switch 174 and does not influence the typewriter 2, and in addition the letter " B " is connected to the " dash " key lever of the typewriter 2 so that a dash is printed when the " B " key is depressed. The key levers of typewriter 1 are reciprocally paired for any selected code setting with the type levers of the typewriter 2 through the discs 40, 41 so that for decoding it is only necessary to swing the switch 174 to the right, thus disconnecting the space bar key of typewriter 1 from typewriter 2, connecting the dash key of the former to the " B " type lever of the latter and the " B " key to the space bar. Code changes may be made as desired by operating the disc 139<a> but the code may be further complicated by changing the connections 33, 34 and 44, 45, between the key levers and the type-lever actuating- solenoids and the discs 40, 41, respectively. The electric motors actuating the typewriters may be driven from an A.C. or a D.C. source of supply but when an A.C. source is used this must be rectified before it can be used to operate the various parts of the device, and a valve rectifier 185 is provided for this purpose ; in addition the switch 23 which is pushed in for D.C. operation thereby connecting the contacts 22, 24, is removed when on a.c. supply, thus permitting the contacts 190, 24 to engage. The two typewriters when not connected together for ciphering purposes may be used in the ordinary way.