GB516088A - Secrecy signalling systems - Google Patents
Secrecy signalling systemsInfo
- Publication number
- GB516088A GB516088A GB20663/38A GB2066338A GB516088A GB 516088 A GB516088 A GB 516088A GB 20663/38 A GB20663/38 A GB 20663/38A GB 2066338 A GB2066338 A GB 2066338A GB 516088 A GB516088 A GB 516088A
- Authority
- GB
- United Kingdom
- Prior art keywords
- cycles
- message
- frequency
- tia
- relays
- 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
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
- H04K1/00—Secret communication
- H04K1/04—Secret communication by frequency scrambling, i.e. by transposing or inverting parts of the frequency band or by inverting the whole band
Landscapes
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Radio Relay Systems (AREA)
- Mobile Radio Communication Systems (AREA)
Abstract
516,088. Secret transmission. STANDARD TELEPHONES & CABLES, Ltd. July 12 1938, No. 20663. Convention date, Aug. 11, 1937. [Class 40 (iv)] [Also in Group XL] In a system in which different messages are sent over the upper and lower sidebands of a carrier, the messages are scrambled and periodically changed from one sideband to the other. If only one message . is being sent, " babble " is fed to the other channel. Two-way transmission is provided and the final modulation is performed in two stages. A schematic arrangement of the system is indicated in Fig. 3. Two channels A, B are each capable of receiving or transmitting, the messages being periodically inverted by the operation of relays such as TIA, TIA<SP>1</SP>. The frequency is shifted through 500, 1250 or 2000 cycles by the operation of a selected one of the appropriate relay group such as TA1, TA2, TA3 and sent out as either an upper or a lower sideband by the energisation of one of the relays as TUI, TLI &c. A typical invertor or frequency shifter is shown in Fig. 5. Four copper oxide rectifiers are connected to form a bridge as shown, the message being connected to terminals 4, 5 and the carrier frequency to terminals 6 and 7. 'The modulation products appear at terminals 8 and 9. If the original band covers say 250- 3000 cycles and the modulation frequency is 3250 cycles, the lower side band, which can be separated by suitable filters, will be 3000-250 cycles and will be an inversion of the original message. The scrambling circuit is indicated in Fig. 4, the relays for the required sequence of changes being energised as cams T1-T6 or R1-R6 are in turn effective. Considering only a transmission message from channel A, the condition of relays TIA, TIA<SP>1</SP> determines whether the message is or is not inverted and then passes through low-pass filter LPF: It enters modulator Mod. TA which is supplied with a frequency of 9500 and the lower side band of the 250-3000 cycle, namely 6500-9250, is passed by filter BPE. The message is then passed to modulator TU or'TL (depending on the operations of TAUL) and supplied with a frequency of 10,000, 10,750, or 11,500 depending on which TS relay is operated. The resulting bands are 750-3500, 1500-4250, and 2250-500 cycles so that a shift of 500, 1250 or 2000 cycles has been made. Band-pass filter BPF passes 750-5000 cycles. 'This scrambled message passes out at J or K, Fig. 6, is modulated and filtered, and recombined, so that the carrier C and bands C + J and C - K are fed to the output channel. This output is twice modulated and filtered, as indicated, before being transmitted by the radio transmitter R.T. Suitable arrangements for receiving and demodulating in stages are described. Specification 366,921 is referred to.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US158464A US2179106A (en) | 1937-08-11 | 1937-08-11 | Secrecy signaling system |
Publications (1)
Publication Number | Publication Date |
---|---|
GB516088A true GB516088A (en) | 1939-12-21 |
Family
ID=22568249
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB20663/38A Expired GB516088A (en) | 1937-08-11 | 1938-07-12 | Secrecy signalling systems |
Country Status (6)
Country | Link |
---|---|
US (1) | US2179106A (en) |
BE (2) | BE429534A (en) |
CH (1) | CH225897A (en) |
FR (1) | FR841895A (en) |
GB (1) | GB516088A (en) |
NL (1) | NL64998C (en) |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB595712A (en) * | 1943-08-02 | 1947-12-15 | Comm Engineering Pty Ltd | Multi-channel telephone systems |
US2490022A (en) * | 1943-09-08 | 1949-12-06 | Tung Sol Lamp Works Inc | Secret signaling system |
BE459652A (en) * | 1944-05-08 | 1945-09-29 | ||
BE473802A (en) * | 1946-08-20 | |||
US2535442A (en) * | 1949-07-26 | 1950-12-26 | James L A Mclaughlin | Heterodyne eliminator communication system |
US2609535A (en) * | 1950-02-06 | 1952-09-02 | Padevco Inc | Multiplex frequency modulation system |
US3011026A (en) * | 1956-05-28 | 1961-11-28 | Zenith Radio Corp | Signal-translating apparatus |
-
0
- BE BE516088D patent/BE516088A/xx unknown
- NL NL64998D patent/NL64998C/xx active
- BE BE429534D patent/BE429534A/xx unknown
-
1937
- 1937-08-11 US US158464A patent/US2179106A/en not_active Expired - Lifetime
-
1938
- 1938-07-12 GB GB20663/38A patent/GB516088A/en not_active Expired
- 1938-08-08 FR FR841895D patent/FR841895A/en not_active Expired
- 1938-08-11 CH CH225897D patent/CH225897A/en unknown
Also Published As
Publication number | Publication date |
---|---|
BE516088A (en) | |
FR841895A (en) | 1939-05-31 |
NL64998C (en) | |
CH225897A (en) | 1943-02-28 |
BE429534A (en) | |
US2179106A (en) | 1939-11-07 |
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