SU809642A1

SU809642A1 - Device for adaptive diversity demodulation of frequency telegraphy signals

Info

Publication number: SU809642A1
Application number: SU792755206A
Authority: SU
Inventors: Николай Михайлович Красуцкий; Владимир Иванович Лобанов; Александр Павлович Пуденков; Юрий Васильевич Шашин; Геннадий Аркадьевич Шутов
Original assignee: Войсковая Часть 25871
Priority date: 1979-04-16
Filing date: 1979-04-16
Publication date: 1981-02-28

Description

Изобретение относится к технике радиосвязи и может использоваться в радиоприемных устройствах, предназначенных для приема сигналов частотной телеграфии. ^{1 * 3} The invention relates to radio communications technology and can be used in radio receivers designed to receive frequency telegraphy signals. ^thirteen

Известно устройство для адаптивной разнесенной демодуляции сигналов частотной телеграфии, содержащее в каждом основном канале полосовой фильтр, выход которого через после- '^υдовательно соединенные усилитель, квадратор, регулируемый усилитель и первый амплитудный детектор подключен ко входу фильтра нижних частот, второй амплитудный детектор, выход 15 которого через выпрямитель соединен с управляющим входом регулируемого усилителя, а в дополнительном канале - первый усилитель-ограничитель, выход которого через последователь- 20 но соединенные полосовой фильтр, второй усилитель-ограничитель и частот-, ный детектор подключен ко входу регулируемого усилителя, управляющий вход которого соединен с выходом выпря- *5 мителя, ко входам которого подключены выходы первого анализатора ошибок и инвертора, при этом входы полосовых фильтров основных каналов соединены со входом первого усилителя-ограничи- 30 теля дополнительного канала, а выхода фильтров нижних частот основных каналов соединены со входами сумматора, выход которого через фильтр манипуляции подключен ко входу первого рещающего блока, выход дополнительного инвертора соединен с управляющим входом второго амплитудного детектора одного из основных каналов и первым входом первого анализатора ошибок дополнительного канала,.и второй решающий блок [1] .A device for adaptive diversity demodulation frequency telegraphy signals comprising each main channel bandpass filter, whose output is the post-through ^'υ sequence coupled amplifier, a squarer, an adjustable amplifier and a first amplitude detector connected to the input of a lowpass filter, a second amplitude detector, yield 15 which through a rectifier is connected to the control input of an adjustable amplifier, and in an additional channel - the first amplifier-limiter, the output of which through a series of 20 an internal bandpass filter, a second amplifier-limiter and a frequency detector are connected to the input of an adjustable amplifier, the control input of which is connected to the output of the rectifier * 5 meter, the inputs of which are connected to the outputs of the first error analyzer and inverter, while the inputs of the bandpass filters of the main channels connected to the input of the first amplifier-limiter of the additional channel, and the output of the low-pass filters of the main channels are connected to the inputs of the adder, the output of which through the manipulation filter is connected to the input of the first a deciding block, the output of the additional inverter is connected to the control input of the second amplitude detector of one of the main channels and the first input of the first error analyzer of the additional channel, and the second decision block [1].

Однако известное устройство имеет низкую верность приема.However, the known device has a low fidelity of reception.

Цель.изобретения - повышение верности приема.The purpose of the invention is to increase the fidelity of admission.

Поставленная цель достигается тем, что в устройство для адаптивной разнесенной демодуляции сигналов частотной телеграфии, содержащее в каждом Основном канале полосовой фильтр, выход которого через последовательно соединенные усилитель, квадратор, регулируемый усилитель и первый амплитудный детектор подключен ко входу фильтра нижних частот, второй амплитудный детектор, выход которого через выпрямитель соединен с управляющим входом регулируемого усилителя, а в дополнительном канале - первый усилитель-ограничитель, выход которого через последовательно соединенные полосовой фильтр, второй усилитель-ограничитель и частотный детектор подключен ко входу регулируемого усилителя, управляющий вход которого соединен с выходом выпрямителя, ко входам которого подключены выходы первого анализатора ошибок и инвертора, при этом входы полосовых фильтров основных каналов соединены со входом первого усилителя-ограничителя дополнительного канала, а выходы Фильтров нижних частот основных каналов соединены со входами сумматора, выход которого через фильтр манипуляции подключен ко входу первого решающего блока, выход дополнительного инвертора соединен с управляющим входом второго амплитудного детектора одного из основных каналов и первым входом первого анализатора ouih-jq бок дополнительного канала, и второй решающий блок, введены дополнительный сумматор и два элемента ИЛИ, причем в каждый основной канал введен элемент задержки, а в дополнительный канал введены фильтр нижних частот, элемент задержки и второй анализатор ошибок, информационный вход которого соединен с информационным входом первого анализатора ошибок и выходом элемента задержки, вход которого соединен со входом регулируемого усилителя, выход которого подключен ко входу фильтра нижних частот, при этом вход инвертора соединен с выходом второго анализатора ошибок, вход которого соединен с управляющим входом второго амплитудного детектора другого основного канала и с выходом первого элемента ИЛИ, к первому входу которого подключен первый выход первого решающего блока, второй выход которого соединен с первым входом второго элемента ИЛИ, вторые входы элементов ИЛИ соединены с выходами второго решающего блока, ко входу которого подключен выход, дополнительного сумматора, входы которого соединены соответственно с выходами первых амплитудных детекторов основных каналов и входом фильтра нижних частот дополнительного канала, а выход второго элемента ИЛИ соединен со входом дополнительного инвертора, причем выход квадратора каждого основного канала через элемент задержки подключен ко входу второго амплитудного детектора, а выход фильтра нижних частот дополнительного канала соединен с соответствующим входом сумматора.This goal is achieved by the fact that in the device for adaptive diversity demodulation of frequency telegraphy signals, containing in each Main channel a band-pass filter, the output of which through a series-connected amplifier, quadrator, adjustable amplifier and the first amplitude detector is connected to the input of the low-pass filter, the second amplitude detector, the output of which through the rectifier is connected to the control input of the adjustable amplifier, and in the additional channel, the first amplifier-limiter, the output of which is black h series-connected bandpass filter, a second amplifier-limiter and a frequency detector connected to the input of an adjustable amplifier, the control input of which is connected to the output of the rectifier, the inputs of which are connected to the outputs of the first error analyzer and inverter, while the inputs of the bandpass filters of the main channels are connected to the input of the first amplifier the limiter of the additional channel, and the outputs of the Low-pass Filters of the main channels are connected to the inputs of the adder, the output of which is connected through the manipulation filter to the input of the first decision block, the output of the additional inverter is connected to the control input of the second amplitude detector of one of the main channels and the first input of the first analyzer ouih-jq side of the additional channel, and the second decision block, an additional adder and two OR elements are introduced, and in each main channel a delay element is introduced, and a low-pass filter, a delay element and a second error analyzer are introduced into the additional channel, the information input of which is connected to the information input of the first error analyzer and the output of the delay element, the input of which is connected to the input of an adjustable amplifier, the output of which is connected to the input of the low-pass filter, while the inverter input is connected to the output of the second error analyzer, the input of which is connected to the control input of the second amplitude detector of the other main channel and with the output of the first OR element, to the first input of which the first output of the first decision block is connected, the second output of which is connected to the first input of the second OR element, the second inputs of the OR elements are connected to the output the second decision block, to the input of which the output is connected, an additional adder, the inputs of which are connected respectively to the outputs of the first amplitude detectors of the main channels and the input of the low-pass filter of the additional channel, and the output of the second OR element is connected to the input of the additional inverter, and the output of the quadrator of each main channel through the delay element is connected to the input of the second amplitude detector, and the output of the low-pass filter of the additional channel is connected to the corresponding input of the total pa

На чертеже представлена структурная электрическая схема предлагаемого устройства.The drawing shows a structural electrical diagram of the proposed device.

Устройство для адаптивной разнесенной демодуляции сигналов частотной телеграфии содержит два основных канала 1, каждый из которых состоит из .30A device for adaptive diversity demodulation of frequency telegraphy signals contains two main channels 1, each of which consists of .30

SOSO

6Q амплитуднонижних часвторого выпрямите10, дополусилителя 2, квадратора 3, регулируемого усилителя 4, первого го детектора 5, фильтра 6 тот, элемента 7 задержки, амплитудного детектора 8, ля 9 и полосового фильтра нительный канал 11, состоящий из первого 12 и второго 13 усилителей-ограничителей, регулируемого усилителя 14, фильтра 15 нижних частот, элемента 16 задержки, первого и второго анализаторов 17 и 18 ошибок соответственно, выпрямителя 19, инвертора 20, полосового фильтра 21 и частотного детектора 22, первый.и второй решающие блоки 23 и 24 соответственно, сумматора 25, первый и второй элементы 26 и 27 ИЛИ соответственно, дополнительный инвертор 28, дополнительный сумматор 29, фильтр 30 манипуляции.6Q of the amplitude of the lower part of the second straighten 10, preamplifier 2, squared 3, adjustable amplifier 4, first detector 5, filter 6 that, delay element 7, amplitude detector 8, a 9 and band pass filter channel 11, consisting of the first 12 and second 13 amplifiers - limiters, adjustable amplifier 14, low-pass filter 15, delay element 16, first and second error analyzers 17 and 18, rectifier 19, inverter 20, band-pass filter 21 and frequency detector 22, first and second decision blocks 23 and 24, respectively , adder 25, the first and second elements 26 and 27 OR, respectively, an additional inverter 28, an additional adder 29, a filter 30 manipulation.

Устройство работает следующим образом.The device operates as follows.

С выхода линейного тракта радиоприемного устройства сигнал по промежуточной частоте поступает на вход двух основных каналов 1 и дополнительного канала 11. После расфильтровки полосовыми фильтрами 10 сигнал в каждом из основных каналов 1 представляет собой чередование посылок и пауз. Этот сигнал усиливается и нормируется в усилителе 2 (усилитель с АРУ), возводится в квадрат в квадраторе 3 и с него подается одновременно на вход регулируемого усилителя 4 и на вход элемента 7 задержки. С выхода выпрямителя 9 поступает управляющее напряжение для регулируемого усилителя 4.From the output of the linear path of the radio receiving device, the signal at an intermediate frequency is fed to the input of two main channels 1 and an additional channel 11. After filtering out with band-pass filters 10, the signal in each of the main channels 1 is an alternation of bursts and pauses. This signal is amplified and normalized in amplifier 2 (an amplifier with AGC), squared in quadrator 3 and fed from it simultaneously to the input of an adjustable amplifier 4 and to the input of the delay element 7. The output of the rectifier 9 receives the control voltage for the adjustable amplifier 4.

Элемент 7 задержки, второй амплитудный детектор 8 и выпрямитель 9 обеспечивают стробирование помех в паузах между посылками сигнала и преобразование их в регулирующее напряжение. Элемент задержки 7 задерживает сигнал таким образом, что при стробировании импульс запрета с запасом перекрывает посылки сигнала тракта. Выпрямитель 9 обеспечивает запоминание уровня помех и преобразование его в регулирующее напряжение не зависимое от соотношения посылок и пауз в сигнале тракта. Взвешенные в регулируемом усилителе 4 импульсы сигнала детектируются первым амплитудным детектором 5, причем в первом канале 1 выделяется огибающая отрицательных полупериодов, а во втором канале 1 ' положительных. Выделенные импульсы подаются одновременно на фильтр 6 нижних частот и дополнительный сумматор 29. С выхода фильтра 6 нижних частот сигналы подаются на вход сумиатора 25.The delay element 7, the second amplitude detector 8 and the rectifier 9 provide gating interference in the pauses between the signal packets and converting them into a regulating voltage. The delay element 7 delays the signal in such a way that, when gated, the inhibit pulse with a margin overlaps the signal paths. The rectifier 9 provides for storing the level of interference and converting it into a regulating voltage independent of the ratio of bursts and pauses in the path signal. Weighted in the adjustable amplifier 4, the signal pulses are detected by the first amplitude detector 5, and in the first channel 1 the envelope of negative half-periods is distinguished, and in the second channel 1 'positive. The selected pulses are fed simultaneously to the low-pass filter 6 and an additional adder 29. From the output of the low-pass filter 6, the signals are fed to the input of the adder 25.

В дополнительном канале входной сигнал усиливается и ограничивается в первом усилителе-ограничителе 12, детектируется в частотном детекторе 22 и поступает одновременно на регу65 лируемый усилитель 14 и на элемент ' 16 задержки. С выхода элемента 16 задержки положительные импульсы подаются на вход первого анализатора ошибок 17, а отрицательные - на вход второго анализатора 18. На другие входы анализаторов 17 и 18 с выхода элемента 26 ИЛИ и дополнительного инвертора 28 подаются импульсы запрета. Выделенные в результате стробирования импульсы дроблений и ошибок подаются на выпрямитель 19 непосредственно и через инвертор 20. Регулирующее напряжение, вырабатываемое выпрямителем 2$ подается на второй вход регулируемого усилителя 14, обеспечивая взвешивание выходных сигналов дополнительного канала 11. С выхода регулируемого усилителя 14 сигналы дополнительного канала 11 посту. пают на вход дополнительного сумматора 29 и через фильтр 15 нижних \ частот на вход сумматора 25. С выхода сумматора 25 сумма сигналов всех трех каналов через фильтр 30 манипуляции подается на вход первого решающего блока 23, а с выхода дополнитель-. ного сумматора 29 на вход второго ре- ‘ шающего блока 24. Решающие блоки идентичны и предназначены для симметрирования и принятия решения о знаке переданной посылки. Положительные импульсы с выходов решающих блоков 23 и 24 подаются на входы первого элемента 26 ИЛИ, а отрицательные на входы второго, элемента 27 ИЛИ. Биполярные импульсы с выхода первого решающего блока 23 подаются к оконечной аппаратуре.In an additional channel, the input signal is amplified and limited in the first amplifier-limiter 12, detected in the frequency detector 22, and fed simultaneously to the adjustable amplifier 14 and to the delay element 16. From the output of the delay element 16, positive pulses are fed to the input of the first error analyzer 17, and negative pulses are fed to the input of the second analyzer 18. Prohibition pulses are sent to the other inputs of the analyzers 17 and 18 from the output of the OR element 26 and the additional inverter 28. The gating and error pulses allocated as a result of the gating are supplied to the rectifier 19 directly and through the inverter 20. The control voltage generated by the rectifier 2 $ is supplied to the second input of the adjustable amplifier 14, providing the weighting of the output signals of the additional channel 11. From the output of the adjustable amplifier 14, the signals of the additional channel 11 post. are fed to the input of the additional adder 29 and through the low-pass filter 15 to the input of the adder 25. From the output of the adder 25, the sum of the signals of all three channels through the manipulation filter 30 is fed to the input of the first decision block 23, and from the output it is additional. the adder 29 to the input of the second decision block 24. The decision blocks are identical and are designed to balance and decide on the sign of the transmitted package. Positive pulses from the outputs of the decision blocks 23 and 24 are fed to the inputs of the first OR element 26, and negative pulses to the inputs of the second, OR element 27. Bipolar pulses from the output of the first decision block 23 are supplied to the terminal equipment.

Элементы 26 и 27 ИЛИ обеспечивают формирование импульсов для обратной связи по решению. Поскольку на входы элементов ИЛИ поступают импульсы, претерпевающие различную временную задержку при их обработке,то выходной сигнал этих схем представляет собой импульсы удлиненные по сравнению с информационными на время, равное разности времени прохождения сигнала.Elements 26 and 27 OR provide the formation of pulses for feedback on the decision. Since the inputs of the OR elements receive pulses that undergo a different time delay during their processing, the output signal of these circuits is pulses elongated in comparison with the information ones by a time equal to the difference in the signal travel time.

Таким образом, предлагаемое устройство позволяет повысить помехоустойчивость приема на 4-6 дБ за счет оптимизации взвешивания выходных сигналов основных каналов, введения фильтрации в дополнительный канал и совершенствования блока анализа ошибок в нем.Thus, the proposed device allows to increase the noise immunity of reception by 4-6 dB by optimizing the weighting of the output signals of the main channels, introducing filtering into the additional channel and improving the error analysis block in it.

Claims

The invention relates to a di-vision technique and can be used in radio receiving devices for receiving frequency telegraphy signals. A device for adaptive diversity demodulation of a frequency telegraphy signal is known, comprising in each main channel a band-pass filter, the output of which is through a serially connected amplifier, a quad, an adjustable amplifier and the first amplitude detector is connected to the input of a low-pass filter, the second Mr. No. 1 is a detector of the output, the output of which is the rectifier is connected to the control input of the adjustable amplifier, and in the additional channel - the first amplifier-limiter, the output of which is through a series-connected A second bandpass filter, a second limiting amplifier and a frequency detector are connected to the input of the adjustable amplifier, the control input of which is connected to the output of the rectifier, to the inputs of which the outputs of the first error analyzer and inverter are connected, while the inputs of the bandpass filters of the main channels are connected to the input the first amplifier is the limited body of the additional channel i- and the low-pass filter outputs of the main channels are connected to the inputs of the adder, the output of which is connected to the input of the first decisive block additional inverter output is connected to a control input of the second kvdim amplitude detector of one of the main channels and the first input of the first supplemental channel analyzer errors .and second decider l. However, the known device has a low fidelity of reception. The purpose of the invention is to increase the fidelity of the reception. The goal is achieved by the fact that in a device for adaptive diversity demodulation of frequency telegraphy signals, in each Main Channel there is a band-pass filter whose output is through a series-connected amplifier, quad, adjustable amplifier and first amplitude detector connected to the input of the low-pass filter, second amplitude detector whose output through a rectifier is connected to the control input of an adjustable amplifier, and in the additional channel - the first amplifier-limiter, the output of which through a series-connected bandpass filter, a second limiting amplifier, and a frequency detector connected to the input of an adjustable amplifier whose control input is connected to the output of the rectifier whose inputs are connected to the output of the first error analyzer and inverter, while the inputs of the bandpass filters of the main channels are connected to the input the first amplifier limits the additional channel, and the low-pass filter outputs of the main channels are connected to the inputs of the adder, the output of which is through the filter connected to the input of the first decision unit, the output of the additional inverter is connected to the control input of the second amplitude generator of one of the main channels and the first input of the first analyzer via an additional channel channel, and the second decision unit, an additional adder and two OR elements are added, each with main the channel has a delay element, and a low-pass filter, a delay element and a second error analyzer, the information input of which is connected to the information input of the first analysis, are added to the additional channel error block and the output of the delay element, whose input is connected to the input of the adjustable amplifier, the output of which is connected to the input of the low-pass filter, while this input of the inverter is connected to the output of the second error analyzer, the input of which is connected to the control input of the second amplitude detector of the other main channel and with the output of the first OR element, to the first input of which the first output of the first decision unit is connected, the second output of which is connected to the first input of the second OR element, the second inputs of the OR elements are connected with the outputs of the second decision block, to the input of which is connected an output of an additional adder, whose inputs are connected respectively to the outputs of the first amplitude detectors of the main channels and the input of the low-pass filter of the additional channel, and the output of the second OR element is connected to the input of the additional inverter, and the output of the quadr each main channel through the delay element is connected to the input of the second amplitude detector, and the output of the low-pass filter of the additional channel is connected to the corresponding the progress of the adder. The drawing shows the structures on the electrical circuit of the proposed device. The device for adaptive diversity demodulation of frequency telegraphy signals contains two main channels 1, each of which consists of silytel 2, quadrant 3, adjustable amplifier 4, first amplitude detector 5, filter 6 lower frequencies, delay element 7, second second detector 8, straighten 9 and band-pass filter 10, an additional channel 11 consisting of first 12 and second 13 amplifiers, adjustable amplify 14, low-pass filter 15, delay time 16, first and second amplifiers 17 and 18 correspond to errors In particular, rectifier 19, inverter 20, band-pass filter 21 and frequency detector 22, first and second decision blocks 23 and 24, respectively, adder 25, first and second elements 26 and 27 OR, respectively, additional inverter 28, additional adder 29, filter 30 manipulation. The device works as follows,. From the output of the linear path of the receiving device, the signal at the intermediate frequency is fed to the input of two main channels 1 and additional channel 11. After filtering out by band-pass filters 10, the signal in each of the main channels 1 is an alternation of parcels and pauses. This signal is amplified and normalized in amplifier 2 (amplifier with AGC), is built in quadrac in quad 3 and is fed simultaneously to the input of adjustable amplifier 4 and to the input of delay element 7. The output voltage of the rectifier 9 is the control voltage for the adjustable amplifier 4. The delay element 7, the second amplitude detector 8 and the rectifier 9 provide gating for interruptions in the pauses between the signals and converting them to the control voltage. The delay element 7 delays the signal in such a way that when gating, the inhibit impulse with a margin overlaps the signal path. Rectifier 9 ensures memorization of the noise level and its transformation into a regulating voltage independent of the ratio of parcels and pauses in the signal of the path. The pulses of the signal, which are weighted in the adjustable amplifier 4, are detected by the first amplitude detector 5, with the envelope of the negative half-periods singled out in the first channel 1 and the positive one in the second channel 1. The selected pulses are simultaneously applied to the low-pass filter 6 and an additional adder 29. From the output of the low-pass filter, signals are fed to the input of Sulmator 25. In the additional channel, the input signal is amplified and limited in the first limiting amplifier 12 and detected simultaneously in the frequency detector 22 on the adjustable amplifier 14 and the element 16 delay. From the output of the delay element 16, positive pulses are fed to the input of the first analyzer of the error box 17, and negative to the input of the second analyzer 18. To the other inputs of the analyzers 17 and 18 from the output of the OR element 26 and the additional inverter 28, the inhibit buttons are also supplied. Gating and error pulses allocated by gating are applied to rectifier 19 directly and through inverter 20. Regulating voltage produced by rectifier i.9 is fed to the second input of adjustable amplifier 14, providing weighting of output signals of additional channel 11. From the output adjustable amplifier 14, additional channel 11, Pstsot channel, to the input of additional adder 29 and through 15 low-pass filter to input of adder 25. From the output of adder 25, the sum of the signals of all three channels through the filter 30 manipulation is input to the first conductive section 23 decide, ac output of the complementary adder 29 to the input D vtorrgo depleting block 24. The decision block ide-particle and are intended to The balance and deciding on the sign of the transmitted package. Positive pulses from the outputs of decision blocks 23 and 24 are fed to the inputs of the first element 26 OR, and negative to the inputs of the second, element 27 OR. Bipolar pulses from the output of the first decision block 23 are fed to the terminal equipment. Elements 26 to 27 OR provide pulse shaping for feedback on the solution. Since the inputs of the OR elements receive pulses that carry different time delays during their processing, the output signal of these circuits is the pulses that are elongated compared to the formation ones for a time equal to the difference in the signal transit time. Thus, the proposed device allows to increase the noise immunity of reception by 4-6 dB by optimizing the weighting of the output signals of the main channels, introducing filtering into the additional channel and improving the error analysis block in it. Apparatus of the Invention A device for adaptively spaced demodulation of signals of frequency telegraphy, containing a bandpass filter in each main channel, output to which through a serially connected amplifier, quad, adjustable amplifier and the first amplitude detector is connected to the input of the lower filter frequency, the second amplitude detector, the output of which through a rectifier is connected to the control input of the adjustable amplifier, and in the additional channel - the first amplifier limiting, the output of which through a series A connected bandpass filter, a second limiting amplifier, and a frequency detector are connected to the input of an adjustable amplifier, the control input of which is connected to the output of the rectifier, to the inputs of which the outputs of the first error analyzer and inverter are connected, while the inputs of the bandpass filters of the main channels are connected to the input of the first the amplifier of the limiting channel of the additional channel, and the low-pass filter outputs of the main channels are connected to the inputs of the adder, the output of which is connected through the manipulation filter to the input of the first the decisive block, the output of the additional inverter is connected to the control input of the second amplitude detector of one of the main channels and the first input of the first analyzer of the additional channel, and a second decision block, characterized in that, in order to increase the accuracy of the reception, an additional adder is added to it and two OR Elements, with each element having a delayed element added to the main channel, and a low-pass filter, a delay element, and a second error analyzer, whose information input connected to the information input of the first error analyzer and the output of the delay element whose input is connected to the input of an adjustable amplifier whose output is connected to the input of the low-pass filter, while the input of the inverter is connected to the output of the second error analyzer whose input is connected to the control input of the second the amplitude detector of another main channel and with the output of the first OR element, to the first input of which the first output of the first decision unit is connected, the second output of which is connected to the first input of the second element OR, the second inputs of the elements OR are connected to the outputs of the second decision unit, the input of which is connected to the output of the additional adder, whose inputs. connected to the outputs of the first amplitude detectors of the main channels and the input of the low-pass filter of the additional channel, and the output of the second element OR is connected to the input of the additional inverter, the output of the quad of each main channel through the delay element is connected to the input of the second amplitude detector channel is connected to the corresponding input of the adder. Sources of information, rintye taken into account in the examination 1. USSR author's certificate, 649163, cl. H 04 L 27 / 14,1977 (prototype).