Patent GB-770512-A (GB)
Title: Electronic transmitter and receiver for signals in a start-stop code
Inventor: SNIJDERS ANTONIE
IPC: H04L25/45
Filed: 1953-03-19
Abstract: 770,512. Code telegraphy. STAATSBEDRIJF DER POSTERIJEN TELEGRAFIE EN TELEFONIE. March 19, 1953 [March 20, 1952], No. 7684/53. Class 40 (3). In an electronic transmitter, for a start-stop code, comprising a number of electronic trigger circuits corresponding to the signal elements and having two stages of stability and arranged in cascade and in which a free-running electronic pulse generator is set into operation by an electronic start-stop trigger circuit in response to a start pulse for a signal, all the signal elements pass into their associated trigger circuits as a result of response to the starting pulse and in response to pulses from the generator are simultaneously transferred to the next electronic trigger circuit by networks comprising a pair of sets of oppositely poled combinations of gated rectifiers via a common input conductor connected to the output of one trigger circuit and a common output conductor connected to the input of the next trigger circuit, the rectifier networks being simultaneously opened by the positive and negative pulses simultaneously derived from a circuit controlled by the generator, so that the elements arrive in succession at the first circuit in the cascade from the output of which potentials representing the signal elements can be derived. In the corresponding receiving arrangement, the received elements are under the control of pulses provided by the generator, applied in succession to one of the trigger circuits and passed in due order through the trigger circuits so that at the end of a signal the elements are stored in the appropriate trigger circuits from the output of which the potentials corresponding to the received signal may be simultaneously derived. The receiving arrangement may be employed as a signal regenerator, the signal elements being taken from the output of the trigger circuit to which the received elements are applied in succession under control of the pulses derived from the electronic pulse generator. The trigger circuits with two conditions of stability comprise a double triode Bla, B1b, and with the triode B1a conducting, the potential at the output terminal 4 is greater than that at output terminal 9. With suitable applied voltages the outputs at terminals 4, 9 are respectively positive and negative when the valve B1a is conducting, and the potentials are reversed when B1a is cut off and B1b made conductive. In the stop condition of the receiver or transmitter, with a positive potential applied at input terminal 7 of the triode B1a of the input trigger circuit, the triode B1a is conducting and a positive potential is present at terminal 4. Additional output terminals 3, 10 are connected to terminals 4, 9 by resistors R9, R6. The start-stop circuit SSS, Fig. 3, and pulse generator G, Fig. 4, comprise double triodes B2a, B2b and B3a, B3b. In the rest condition of the receiver a negative potential is applied at terminal 8 to the grid of the triode B2a so that B2b conducts and the control grid of the triode B3a has the same negative potential that it has if, during the operation of the generator, the triode B3a is non-conductive. The triode B3b is conductive and the capacitors C1, C2 are charged to equal values. If the triode B2a is made conductive, the triode B2b cut off, capacitor C1 discharges and the grid voltage of the triode B3a rises. After a period of 10 ms. to allow for " false-start suppression," the triode B3a becomes conductive and the triode B3b cuts off, producing a positive pulse at the output terminal 3. After a further 10 ms. the triode B3b becomes conductive again and the triode B3a is cut off and 10 ms. later B3a conducts so that B3b cuts off and produces a positive pulse at 30 ms. The generator continues to operate until cut off by a negative potential applied to the grid of the triode B2a. In the receiver circuit, Fig. 7, the component elements IS, IV, GSI ... GSVII are bistable trigger circuits as shown in Fig. 2, the terminals 5 and 7 of the elements GSI ... GSVII being connected together so that they remain in the condition to which they have been triggered after the controlling voltage has been removed. In the rest condition a positive polarity is applied at the input terminal I and the trigger circuits GSI, GSVII are respectively in the negative and positive states. The junction point a which is connected to the terminals 9 of IS and GSI and assumes the more negative of the potentials at those outputs is at a negative potential and point b which assumes the more positive voltage of the points a and the terminal 4 of GSI is also negative so that the start-stop circuit SSS is ineffective. When the start element is received, the trigger circuit IS is changed over so that the output at terminal 9 is positive. The point a and consequently the point b become positive so that the circuit SSS is set into operation. If the start element persists for 10 ms., the generator G provides a positive impulse from its terminal 3 triggering circuit GSI to the positive state in which its output terminal 3 applies a positive pulse to the junction of resistors R44, R45 and to the inputs of GSII ... GSVI which now assume the positive state. At the same time the negative pulse from terminal 10 is applied to the junction of R42, R43 and to the input of GSVII which is triggered to the negative state. Whilst GSI remains in the positive condition the point b is positive, irrespective of the pulses received at the input terminal I, and the start-stop circuit SSS maintains the generator G in operation. At the end of 30 ms. the generator G provides a positive pulse which triggers the circuit IV to the positive state in which positive and negative pulses simultaneously appear at the terminals 4, 9 respectively and are applied to the positive and negative terminals of similarly poled rectifier networks, such as G61, G63, G66 and G62, G64, G67 associated with GSVII, so that the gating circuit is opened and the condition of the trigger IS in response to the first signal element received at the terminal I is passed from terminal 4 to the input 7 of the trigger GSVII which assumes the corresponding condition. Further, the element stored on the trigger GSVII is passed from its output terminal 4 to the input of the rectifier network G52, G54, G56 and G53, G55, G57, the output of which from the junction of the rectifiers G52, G53 is passed to the input terminal 7 of the circuit GSVI. At the end of 130 ms. the received elements are stored on the terminals II ... VI of the triggers GSII ... GSVI, the trigger GSVII is in the positive condition and the negative condition exists on the trigger GSI so that the point a becomes negative and the point b also changes to negative since the output terminal 4 of GSI becomes negative. The start-stop circuit changes over so that the generator G is inoperative. If desired, the signal elements as they are received and stored can be taken from the terminal VII connected to the terminal 4 of the trigger GSVII so that the arrangement acts as a regenerator of the received signals. The receiver includes an arrangement to prevent the trigger GSVII from assuming the negative condition during the " at rest " condition of the receiver even if the input terminals were accidentally at negative during that period. Another circuit arrangement is included to prevent all the trigger circuits GSI ... GSVII from assuming the positive condition which might occur when the apparatus was initially switched on, and which would result in the receiver running continuously. Transmitter. In the modified arrangement, Fig. 9 (not shown), constituting an electronic transmitter, the persistence of a starting pulse for 10 ms. results in the pulse generator being started into operation, and the code combination of the five elements to be transmitted is applied simultaneously to the 2nd ... 6th triggers of the series, the 1st and 7th triggers being changed over to the conditions representing the start and stop elements respectively. At 30 ms. a pulse derived from the generator causes pulses to be generated to open the gating rectifier networks with the result that the pattern is stepped, the first trigger is conditioned according to the first significant element of the code combination, the second trigger is set according to the second element, and so on. The code combination to be transmitted is taken from the output terminal 4 of the first trigger circuit of the array. The transmitter also includes an arrangement to prevent the first trigger circuit of the cascaded array from assuming the negative or start condition in the rest condition of the transmitter.