Patent GB-793104-A (GB)
Title: Station identification signal keyer for use in ground aviation trainers
IPC: G09B9/26
Filed: 1954-07-21
Abstract: 793,104. Code telegraph transmitters. LINK AVIATION, Inc. July 21, 1954 [July 22, 1953]; No. 21324/54. Class 40 (3). Apparatus used in connection with the training of pilots or operators for automatically transmitting call signs constituted by a number of characters representing a station, comprises a number of selector switches each of which can be set according to any desired character and by which an operator can select the predetermined characters of the call sign and each selector switch produces voltages having amplitudes which are commensurate with the time duration of the dot and dash elements of the predetermined code character selected by the switch and which are fed to a circuit by which the signals elements and the time intervals between them are transmitted. The characters to be transmitted are set up on three selector switches 200, 202, 204 having rotatable members 200e, 202e, 204e engaging contacts designating the various letters or characters and connected to dot and dash conductors 206, 208 of the four switch members 200a, 200b ... 200d, 202a ... 202d, 204a ... 204d according to the 1st, 2nd, 3rd and 4th elements of the Morse code representing the character. The switches 200 ... 204 have fifth banks 200g ... 204g comprising a rotatable member 200e ... 204e engaging a terminal corresponding to the selected character and the terminals are interconnected so that connections are made for characters of equal time duration by conductors 228 ...240 to sections of a potentiometer formed by a series of resistors 214 ... 226. The effective time durations of the three character signals as designated by the potentiometers 214 ... 226 are applied by brushes 220f ... 204f to equal summing resistors 242 from which a voltage representative of the total time required for the three characters is passed to a conductor 244 connected over a switch 246 to the dash conductor 208. The switch in its upper position sets a predetermined time for the transmission of the three characters irrespective of their formation by dots and dashes. The switch in its alternative position connected in series with the resistor 247, sets predetermined times for the transmission of the elements (dot, dash) of the character, and this may be varied by the potentiometer 251. The dash voltage appearing on the conductor 208 is tapped by a potentiometer 300, 302 so that the voltage appearing on the dot conductor 206 is one third that appearing on the conductor 208. When the operation of the apparatus is initiated, and potential is applied over conductor 178 by contacts 100 closed by cam 102, a relay E operates and releases a silence relay 106, and transfers an earth connection from the suppressor grid of a valve 108 to its cathode. The screen voltage of the valve 108 is increased and supplied to the grid of a valve 110 which conducts and operates a relay 112 which at contact 1 earths the suppressor grid of silence tube 114 and at contact 2 energizes a keying relay X which at contact 3 connects an oscillator OSC to earphones 50. The operation of relay X opens the circuit of relay D which releases and operates relay Z. The voltage on the selected contact of the first bank 200a is connected by brush 200f to the sound control tube 172 and also to an index control tube 174 controlling an index relay 176 which is energized and operates relay A. When the sound tube 108 operates, its plate voltage decreases until it reaches the level set on the plate of tube 172 by the dot or dash voltage appertaining to the first element of the first character. The valve 108 integrates until its plate voltage equals that of the plate of control tube 172 and then cuts off tube 110 releasing the sound relay 112 and again operating the silence tube 114 of which the screen voltage increases causing the tube 182 to conduct and to operate silence relay 106 which renders the sound tube 108 inoperative. A voltage equal to the dot voltage is passed over released contact D1 to the plate of a silence tube 184 and the tube 114 operates until its plate voltage drops to the level of that applied to the tube 184 at which level the voltage on the grid of valve 114 shuts off tube 182 releasing the silence relay 106 and again operating the sound tube 108 to energize sound relay 112 with operation of relay X and the connection of the oscillator OSC to the earphones for the period of a dot or a dash. At the end of the transmission of the first character, the relay X, A, B, Y are all released and the relays D, F, Z, V, E are all operated. Relay D connects the dash voltage from conductor 208 through closed contact 1 to the plate of tube 184 and the silence tube 114 operates to provide a character space of dash duration. At the end of the silence period relay X is again operated to connect the oscillator OSC and releases relays D, F, but relay E remains operated and with V operated and B released, the voltage of the first element of the second character as set up in the bank 202a is applied to the control tube 174 and the plate of the control tube 172 so that the sound tube 108 operates for a period corresponding to a dot or a dash. At the end of the second letter, if the switch 116, Fig. 6, is in the two-letter position, the relay E releases the index relay 176 and the apparatus remains inoperative until the switch 100, Fig. 5, is again operated by the rotating timing cam 102. If the switch is in the threeletter position relay E is not released until the end of the third character. If any letter has less than four elements, the contact of the bank 200b, 200c, 200d or the contact on the corresponding banks of the switches 202, 204, following the last element of the character, is connected to earth. The " E " terminal of bank 200b is earthed and its connection to the grid of the tube 174 cuts off the tube and releases relay 176. The circuits of relays A, B, V are opened and relay D is operated as at the end of each letter so that a dash voltage is applied to the silence tube to give character spacing. Relays F, V which are still operated in combination with relay D examine the bank contacts of the selector switch 202, and the dot or dash voltage from the bank 202a re-operates the tube 174 and the relay 176.