US2397885A - Frequency diversity telegraph system - Google Patents

Frequency diversity telegraph system Download PDF

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Publication number
US2397885A
US2397885A US492788A US49278843A US2397885A US 2397885 A US2397885 A US 2397885A US 492788 A US492788 A US 492788A US 49278843 A US49278843 A US 49278843A US 2397885 A US2397885 A US 2397885A
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US
United States
Prior art keywords
currents
marking
spacing
current
signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US492788A
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English (en)
Inventor
Rhodes Harold Anson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AT&T Corp
Original Assignee
American Telephone and Telegraph Co Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to BE475946D priority Critical patent/BE475946A/xx
Application filed by American Telephone and Telegraph Co Inc filed Critical American Telephone and Telegraph Co Inc
Priority to US492788A priority patent/US2397885A/en
Priority to US566079A priority patent/US2407684A/en
Application granted granted Critical
Publication of US2397885A publication Critical patent/US2397885A/en
Priority to FR977847D priority patent/FR977847A/fr
Priority to GB21761/47A priority patent/GB654253A/en
Priority to NL135246A priority patent/NL91653C/xx
Priority to GB5096/48A priority patent/GB654271A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
    • H04L1/04—Arrangements for detecting or preventing errors in the information received by diversity reception using frequency diversity

Definitions

  • 'I'his invention relates generally to signaling systems, and more particularly to telegraph systems. lates to two-tone 'telegraph systems, as well-as to frequency diversity telegraph systems employing either wire line, radioor other transmission media.
  • the limiter will introduce noise and eiitraneous currents and transmit these undesired currents to the telegraph receiving urelay. Hence the signals may become distorted and perhaps rendered unintelligible.
  • each marking signal will be conveyed by a low frequency current and by a high frequency current resulting from modulation and each spacing signal will likewise be conveyed by a low frequency current and by a high frequency current resulting from modulation.
  • each spacing signal will likewise be conveyed by a low frequency current and by a high frequency current resulting from modulation.
  • the two higher frequencies resulting from modulation at the transmitter will be reduced in the frequency spectrum by demodulation with current of a common oscillator.
  • the two currents of different Still more particularly, this invention resignals.
  • the two currents corresponding to each marking signal will then be combined and detected to actuate a common telegraph receiving relay and likewise the two currents corresponding to each spacing signal will be thereafter combined and detectedvto actuate the same telegraph receiving relay. 4Thus the telegraph receiving relay will reproduce the marking and spacing-signals originating at the transmitting station.
  • each marked signal will cause the production of current of one frequency and each spacing signal will cause the production of current of a dierent frequency.
  • each marking signal will cause the production of current of a dierent frequency.
  • these same currents will be transmitted over one path, while over another path these same currents will be modulated upon current of a different frequency to produce the two higher frequencies corresponding to the same signais, as already noted.
  • the transmitter of the system will produce current of one frequency and a modulation product of a higher frequency in accordance with each marking signal, and current of a different frequency and a modulation product of a higher frequency in accordance with each spacing signal, as mentioned above.
  • the two lower frequencies which correspond to the marking and spacing signals respectively
  • the two higher frequencies which also correspond to the same marking and spacing signals respectively
  • the currents corresponding to the marking signals traversing both paths will be combined, amplified, then limited in amplitude and detected.
  • the remaining currents corresponding to the spacing signals will also be combined, amplified and limited in amplitude and thereafter detected.
  • the refer- 'ence character on represents a low frequency oscillation generator which supplies current to a plurality of. devices 011-023, all of which may 4produce different harmonics of the current of the oscillator On. If the oscillator Oo generates current of, for example, 85 cycles per second, the devices O11 and O12, may produce the two harmonics or tones of, for example, 425 and 595 cycles per second respectively, for transmitting the marking and spacing signals of one of the telegraph channels. The otherldevices Oia-Osa may similarly produce still higher harmonics of the same base frequency of oscillator Oo for transmitting the marking and spacing signals of other telegraph channels. To simplify'the description, all of these devices 011-023 will be referred to hereafter as oscillators.
  • the apparatus 'for controlling the oscillators O11 and O12 for one of the channels is shown in Fig. 3.
  • the key ⁇ K1 may be closed to operate the relays R1 andl Rz.
  • the key K1 is closed in accordance with a marking signal, the. armatures of both relays R1 and Rz will move to their marking contacts M so that the oscillator O11 will freely transmit its current, while the current of oscillator O12 will be'suppressed by the shunt circuit established by the armature and contact M of relay Ra around this oscillator.
  • the relay armatures When key K1 is opened in accordance with a spacing signal, the relay armatures will close their spacing con'- tacts S, in which case the oscillator 011 will freely transmit current while the current 4of oscillator O11 will be suppressed.
  • the oscillators 01s and O14 will be controlled by the marking or spacing signals of another telegraph channel, oscillators 01s and 01e will be similarly controlled by the marking or spacing signals of a third telegraph channel, and so on.
  • the oscillator O2 may be used for supplying current for an order circuit, but in this case the current of oscillator 02s may be interrupted in accordance with marking and spacing signals.
  • All of the oscillators 011 to Oi are connected to telegraph sending circuits designated SSu to SS23- and to filters F11 and F23, respectively, each pair of telegraph sending circuits SS11 to SSzzvbeing of the type shown in Fig. 3, and designed to freely transmit only the currents of the 'associated oscillators O11 to O22, respectively, as already mentioned with regard to Fig. 3.
  • the sending circuit SScs may be of a simple type employing a key m for interrupting the current of oscillator O23.
  • the outputs of all of the filters F11 to F23 are connected to a common bus CB1, which receives all of the currents of both marking and spacing signals of all of thetelegraph channels.
  • 'I'he common bus CB1 is connected through a line L1 to two paths, the upper of which extends to a low pass filter F31 and the other includes an amplifier A1 and a modulator MD and extends to a high pass lter F32.
  • the modulator MD is supplied with current from another oscillator Oso, which is also connected to the base frequency oscillator Oo, the oscillator asoman Oan producing a still higher harmonic of the current of oscillator Oo of. for example, 5,270 cycles.
  • the filter F31 is of the low pass type-and is employed to transmit the currents of oscillators O11 to On, extending over a range of from 425 to 2,465 cycles, for example, while the lter Fas is of the high pass type and willtransmit thesel same currents raised in the frequency spectrum as a result vof modulation by the modulator MD.
  • the currents transmitted by filter Fai may'extend from, for example, 2,805 to 4,845 cycles.
  • the currents transmitted by both filters F31 an ⁇ d F32 will be amplied by amplifier A: and then radiated through space by a radio transmitter RT, which is supplied witha high or radio frequency current generated by an oscillator y0:11.
  • the marking and spacing signals corresponding to the first of the telegraph channels will be transmitted by oscillators O11 and O12 in accordance with the two-tone method, and these currents will be transmitted by the low pass filter Fn, while these same currents will be raised in the frequency spectrum by modulator MD for transmission through the high" pass filter F32. If the oscillators 0 11 and O12 produce currents of 425 and 595 cycles, as already stated, the modulation currents corresponding to the same signals produced by modulator MD and transmitted by lter Fan will have frequencies of 4,845 and 4,675 cycles.
  • These four -currents are employed for frequency diversity to convey the marking and spacing signals of but one telegraph channel, the currents of 425 and 4,845 cycles corresponding to a marking signal and the currents of 595 and 4,675 cycles corresponding tota spacing signal.
  • the signals received by the radio receiver RR of Fig. 2 are demodulated by a locally produced current emanating from oscillator 04o.
  • the demodulated currents are then amplified by ampliyfier Aa and then divided into two bands, one of which is selected and transmitted by the low pass vselectively transmitting currents having the frequencies of oscillators 011 to O23, respectively'.
  • the output circuit of filter F411 is connected to a demodulator DM which is supplied with the current of an oscillator 041 for demodulating the received currents in the higher portion of the range so as to reduce these currents to lower frequencies.
  • the lower frequencies resulting from demodulation extend from 765 to 2805 cycles.
  • These currents are amplified by amplifier A4 and are then impressed upon a common bus CBs.
  • the common bus CB is bridged by filters F61 to Frs, which correspond to filters F11 to Fas and their respective oscillators O11 to 02s at the transmitting station.
  • the output circuits of filters F41 and F42 are connected to each other and supply the low frequency marking and spacing currents alternately to a hybrid network HN for telegraph channel l.
  • the filters F61 and Fea are also connected to each other and supply the higher frequency marking and spacing currents to the same and connected to an amplifier As.
  • filters Fn and Fez may transmit, for example, currents of '765 and 925 cycles. combines these currents as received, the combined currents are then amplified by a common ampliiler As, and the amplified currents are transmitted through a common current limiter CL.
  • the output circuit of -limiter CL is bridged by four filters designated Fai, Far. For and Fn.
  • the i'llters F111 ⁇ and F91 may be the same as the filters F41 and F61, respectively, and filters Fan and-F92 may be the same as filters F42 and Fez.
  • the filters Fei and F91 will transmit currents of two different frequencies corresponding to a single marking signal, and filters Fs: and F92 will transmit currents of. two different frequencies corresponding to a single spacing signal.
  • 'I'he filters F51 and F91 are connected to each other and to a detector D1 which detects the currents corresponding to a marking signal.
  • the filters Fan and Fez are connected to each other and to a detector D2 which detects the currents corresponding to a spacing
  • the relay Rs connected to both detectors may transmit the signals to a teletypewriter TTY,
  • the o'rder circuit marking and spacing signals which are of the invention embodies a frequency diversity system in which two currents of different frequencies, such as 425 cycles and '165 cycles perfsecond, transmitted in accordance with each marking signal, and two currents of still other frequencies, such as 595 cycles and 935 cycles per second, transmitted in accordance with each spacing signal, are impressed upon the common limiterlCL.
  • the limiter GL accentuates the stronger of the two marking currents while effectively suppressing the weaker marking current and, moreover, the limitery CL accentuates the stronger of the two spacing currents while effectively suppressing the weaker spacing current.
  • the amplitude of the 765 cycle marking current exceeds the amplitude of the 425 cycle marking current
  • the stronger '165 cycle marking current will be effectively selected by thel limiter CL while the weaker 425 cycle marking current will be effectively suppressed along with any extraneous noise present.
  • the stronger spacing current will be effectively selected bythe limiter CL and the weaker spacing current and extraneous noise will be effectively suppressed.
  • the filters Fa1, Fez, F91 and Fez connected in parallel to the limiter CL, act to transmit the stronger marking and spacing currents, whichever they may be, to detectors D1 and Dz. If the 765 cycle marking currentis the stronger, it will be transmitted by filter F111 and detected by detector D1. Likewise, if the 595 cycle yspacing current is the stronger, it will be transmitted by filter Fez and detected by deteci301' D2.
  • the making currents will be interspersed with the spacing signalsso that in general either the marking currents or the spacing currents always will be present and acted on by limiter CL.
  • the other marking current will be effectively selected by the limiter CL to transmit a strong marking signal.
  • the appropriate filter connected to the output circuit of the limiter will pass a strong marking signal to the detecor Di to actuate the relay R3.
  • the limiter CL will perform in the same' manner When one of the spacing currents of the channel becomes faded, the limiter acting to produce a strong spacing signal.
  • a telegraph signaling system the combination of means for producing currents of two frequencies in accordance with each marking signal and currents of two other frequencies inaccordance with each spacing signal, an amplifier for amplifying all of said currents, a limiter connected to said amplifier, the limiter acting to effectively suppress the weaker of the two currents corresponding to each marking signal as well as the weaker of the two currents corresponding to each spacing signal, means connected tosaid limiter for separating the different currents from each other, two detectors one for detecting the stronger of the two currents corresponding to eacli marking signal and the other for detecting the stronger of the two currents corresponding to each spacing signal, and means for reproducing the marking and spacing signals from said detected currents.
  • receiving means including means for obtaining currents corresponding to said irst frequencyand its modulation prod- -uct for each marking signal and currents corresponding to said second frequency and its modulation product for each spacing signal, a limiter i or effectively suppressing the weaker of the currents corresponding to'said marking and spacing signals, and means for detecting the stronger currents corresponding to each marking signal separate from the strongercurrents corresponding to each spacing signal.
  • each marking signal and each spacing signal consisting of currents of a plurality of different frequencies, a limiter through which all oi said currents are transmitted, a plurality of filters for separating each current from all other currents, two detectors, one "detector being connected to all of the illters passing currents Vcorresponding to a marking signal and the other detector being connected to all of the filters passing currents corresponding to a spacing signal,'

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Reduction Or Emphasis Of Bandwidth Of Signals (AREA)
  • Radio Transmission System (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
US492788A 1943-06-30 1943-06-30 Frequency diversity telegraph system Expired - Lifetime US2397885A (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
BE475946D BE475946A (is") 1943-06-30
US492788A US2397885A (en) 1943-06-30 1943-06-30 Frequency diversity telegraph system
US566079A US2407684A (en) 1943-06-30 1944-12-01 Radio communication system
FR977847D FR977847A (fr) 1943-06-30 1947-07-31 Dispositif de radio-communication
GB21761/47A GB654253A (en) 1943-06-30 1947-08-07 Improvements in or relating to radio telegraph communication systems
NL135246A NL91653C (is") 1943-06-30 1947-10-07
GB5096/48A GB654271A (en) 1943-06-30 1948-02-20 Improvements in or relating to telegraph systems

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US492788A US2397885A (en) 1943-06-30 1943-06-30 Frequency diversity telegraph system
US566079A US2407684A (en) 1943-06-30 1944-12-01 Radio communication system

Publications (1)

Publication Number Publication Date
US2397885A true US2397885A (en) 1946-04-02

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Application Number Title Priority Date Filing Date
US492788A Expired - Lifetime US2397885A (en) 1943-06-30 1943-06-30 Frequency diversity telegraph system
US566079A Expired - Lifetime US2407684A (en) 1943-06-30 1944-12-01 Radio communication system

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Application Number Title Priority Date Filing Date
US566079A Expired - Lifetime US2407684A (en) 1943-06-30 1944-12-01 Radio communication system

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US (2) US2397885A (is")
BE (1) BE475946A (is")
FR (1) FR977847A (is")
GB (2) GB654253A (is")
NL (1) NL91653C (is")

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2507730A (en) * 1946-05-16 1950-05-16 Rca Corp Frequency shift receiver
US3037080A (en) * 1960-06-07 1962-05-29 Schindler Ludwig Telecommunication receiver

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2495997A (en) * 1944-10-31 1950-01-31 Philco Corp Radio receiver aligning apparatus and method
US2455996A (en) * 1945-12-15 1948-12-14 Rca Corp Frequency modulated radio testing system
US3045071A (en) * 1956-11-13 1962-07-17 Decca Ltd Electrical transmission and storage of information represented by direct voltages
CH350011A (de) * 1957-02-21 1960-11-15 Siemens Ag Albis Schaltungsanordnung zum Übertragen von Nachrichten über Fernschreibvermittlungsanlagen
US4335464A (en) * 1980-01-24 1982-06-15 Paradyne Corporation Dual multipoint data transmission system modem

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2507730A (en) * 1946-05-16 1950-05-16 Rca Corp Frequency shift receiver
US3037080A (en) * 1960-06-07 1962-05-29 Schindler Ludwig Telecommunication receiver

Also Published As

Publication number Publication date
FR977847A (fr) 1951-04-05
US2407684A (en) 1946-09-17
NL91653C (is") 1959-08-15
BE475946A (is")
GB654253A (en) 1951-06-13
GB654271A (en) 1951-06-13

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