US1912983A - Secret telegraph system - Google Patents

Secret telegraph system Download PDF

Info

Publication number
US1912983A
US1912983A US551206A US55120631A US1912983A US 1912983 A US1912983 A US 1912983A US 551206 A US551206 A US 551206A US 55120631 A US55120631 A US 55120631A US 1912983 A US1912983 A US 1912983A
Authority
US
United States
Prior art keywords
arrangement
contacts
contact
impulse
combination
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
US551206A
Other languages
English (en)
Inventor
Jipp August
Rossberg Ehrhard
Hettler Eberhard
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.)
Siemens and Halske AG
Siemens AG
Original Assignee
Siemens AG
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
Application filed by Siemens AG filed Critical Siemens AG
Application granted granted Critical
Publication of US1912983A publication Critical patent/US1912983A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
    • H04L9/38—Encryption being effected by mechanical apparatus, e.g. rotating cams, switches, keytape punchers

Definitions

  • Another object of our invention is to provide special kinds of coding or ciphering.
  • a further object of our invention is to pro- I vide a double coding of a special kind by which an unauthorized deciphering of the coded message is rendered dilficult.
  • a still further object of our invention is to apply the improved secret telegraph system to such apparatus which is equipped with a substantially mechanically operating receiver which cannot be made use of for decoding.
  • a still further object of our invention is to provide special improved constructions of coding and decoding apparatus.
  • the sign to be telegraphed is translated into a combination of electric impulses which is then electrically transmitted.
  • keys of a keyboard of the trans mitter selector bars are in a mechanical manner adjusted in such a way that they are dis placed in the direction of their length'by a certain amount.
  • These selector bars control the contacts assigned to the individual impulse elements of the sign combination. According to the position of these contacts a circuit is either broken or made by the individualimpulses, or each individual impulse is represented either by a positive or negative rush of current.
  • the contacts adjusted by the combination or selector bars are in succession tapped by a suitable contact mechanism and the combination of impulses dis patched thereby.
  • a mechanism for coding which changes its adjustment during the transmission of the signs, and by which the current values of the individual impulses of the sign combination are changed before dispatch and/or the sequence of the dispatch of the individual combination elements is interchanged.
  • the coding mechanism consists of sets of springs by the operation of which the coding is effected and code discs which control the said sets of contact springs.
  • code discs may, for instance, be cams of any suitable design which are either rotatable on a common axis or shaft, or they may be connected by means of a ratio gear so as to have different relative speeds.
  • the drive of these code arrangements may likewise be chosen differently by providing' either a purely mechanical or also an electromechanical driving possibility.
  • a fresh settin of the entire arrangement according to def nite characteristics, for instance by means of a code, in. certain intervals presents the possibility of varying the code still further.
  • the signals transmitted by the transmitter are across the contacts conveyed to a decoding mechanism. operating and. set according to the transmitting code equipment or to the receiving relay of the telegraph apparatus according to the nature of the receiver, whereby. the secret combination is decoded.
  • a special advantage of our invention resides in the fact that the deoding at the receiver is efi'ected by means of a mechanism which by its suitable construction according to the nature of the telegraph apparatus employed may either be directly incorporated into the apparatus, since parts of the decoding mechanism may also 'be directly employed for thetranslation of the signal combinations into the sign to be printed, or parts of the standard receiver may be made use of for the decoding, which is mainly applicable for electrically operating apparatus. If
  • FIG. 1 is a diagrammatic representation of a transmitting apparatus known per se combined with a coding mechanism according to our invention. Of the transmitter only the details cooperating with the coding mechanism are shown,
  • Fig. 2 represents the apparatus at the receiving end, and more particularly a decoding mechanism connected ahead of or in series with the receiver of known design
  • Figs. 3 and 4 represent in principle the changes of the contact sets of a special interchanging arrangement.
  • T is the keyboard of a standard start-stop printing telegraph apparatus as described in the Text Book of Communications by A. E. Stone published by Mac Millan and Co. Ltd. (London 1928) on pages 288 to 293.
  • the selector bars 1 to 5 which on depressing a key lever, for instance the key lever Te shown, are shifted towards one side or the other in accordance with the combination of signals in question.
  • the signal key mechanism of which operates on a mechanical principle these selector bars actuate or shift the contacts or switches is, to in engagement with them directly, whereupon on rotation of the simultaneously started tapping cam shaft these contact positions are electrically tapped.
  • the teeth out into the selector bars are only shown by way of illustration.
  • a bar 6 arranged in a similar manner which on depressing a key lever is shifted in one direction only and in doing this closes the contact ak.
  • a starting circuit for the starting relay AR is completed which across its contact an energizes the magnet AM of the start-stop coupling AK so that the start-stop shaft SW with the tapping discs F to F. for tapping the adjusted combination of signals performs one revolution.
  • the start-stop coupling AK couples the shaft SW with the continuously revolving shaft MW which through a worm gear is connected with the driving motor of the telegraph apparatus.
  • the contacts 70 to I0 operated by the selector bars are designed as shift contacts and are by means of the upper and lower contact springs connected with further contacts 1, to 5, designed as double shift contacts which are adapted to be operated by a special cam arrangement.
  • This cam arrangement is in Fig. 1 designated by the reference character CT and serves to bring about the interchange of the impulse values of a combination set by the selector bar arrange ment T.
  • the cams N N and so on controlling these contacts we have, for the sake of clearness, only'shown those for the shift contacts 1. and 2 which'correspond with the first and second sign elements of a combination of letters.
  • These cam discs N N and so on are dissimilar and provided with different numbers of cam faces which, furthermore, are irregularly distributed over the periphery of the discs.
  • the contacts 10 to 10 are with their central springs connected to the operating means of the interchanging or jumbling mechanism CW by lines l to Z...
  • the individual conduc tors of the impulse elements are interchanged with one another so that a variation in the sequence of the various elements of a combination is obtained.
  • a set of contacts consisting of two shift contacts, whereby one conductor takes the place of the other and vice versa on reversing the contacts. The number of these sets of. contacts follows from the interchange possibilities of the 5 conductors of a five impulse combination.
  • FIGs. 3 and 4 there are diagrammatically shown examples for the number and for the arrangement of the sets of contacts of such an interchange arrangement. Only the set of contacts 1w corresponding with the terchange of the same and thus corresponds.
  • Fig. 4 there is illustrated'a further principle for obtaining all the interchange or permutation possibilities with only ten sets of contacts.
  • the normal position of a set of contacts is indicated by the crossing lines and the interchanging position by the broken lines representing the parallel course of the connecting conductors.
  • This representation of the principle also shows that a certain conductor; for instance the conductor 1 in Fig. 3 can only be interchanged with conductors immediately adjacent to it in the impulse sequence, for in- I stance with the conductors 2-and 5 by the contact sets 1w and 6w.
  • any one conductor is connected with all further conductors of the combination by a single contact operation at a time.
  • a simultaneous and selective operation of a plurality of such sets of contacts the'most diversified exchange possibilities may be brought about.
  • Fig. 1 of the drawings only 2 sets of contacts are illustrated for the sake of simplicity and clearness which are connected according to the interchange principle of the Fig. 3 described above and which are identical with the sets of contacts 1w and 6w of the same figure. Across the sets of contacts 1w are thus taken the'connecting conductors Z and Z which can be interchanged one with the other b throwing-over this contact towards the eft.
  • the contact 4 is closed across which is taken the conductor Z in exactly the same manner there is' closed the contact 2 for the conductor Z on interchanging these two conductors the contact 4 is opened for the conductor L, for instance, so that now this conductor takes the place of the conductor 2- across the closed contact 1 and vice versa the conductor Z takes the place of the conductor 1 across the closed contact 3.
  • the set of contacts 6w is shown in a position in which the conductor Z is interchanged with the conductor Z As already explained in connection with the set of contacts 1w, the conductor Z passes across the closed contact 1, while the conductor Z by the connection of the closed contact 3 takes the place of the conductor Z.
  • the sets of contacts of this arrangement CW are controlled by cams, for instance N10 for the set of contacts 110 and Nw for the set of contacts 6w, which are designed in a similar manner to the cams of the arrangement CT described above.
  • the contacts otthe arrangement DCW are controlled by the cams 1 NW (Nw to Nw the contacts of the arrangement DCT by the cams N (N N and so on) in correspondence with the control by the respective cams at the transmitting end.
  • These cams are intermittently advanced by means of a common driving shaft AlV, as at the transmitting end, diiferent speeds for the cams being attained again by dill'erent trans-. mission ratios'ot the driving wheels.
  • a resetting also takes place after receipt of a combination of slgns or signals.
  • the cams which correspond in the transmitting and receiving apparatus are, as regards their cam faces and their stepping speed, exactly 1dentical so that after-prior coinciding adjustof the contact in the individual contact arrangements. In this way the double coding caused in the transmitting apliaratus is neutralized againin the receiving apparatus.
  • the individual connecting conductors Z to Z (Fig. 2) corresponding with the individual impulse elements must traverse the sets of contacts of the arrangement DCWV in the reverse order or mirror reading, as compared with the sequence in the transmitter.
  • a transmitting arrangement which contains in combination an arrangement for setting electric current combinations of the signs to be transmitted, a coding arrangement adapted to change its setting during th transmission of the sign in order to code the set electric current combin ations by direct means, without the interposition of relays, before the dispatch of the sign combinations commences, said coding arrangement including a plurality of contact elements corresponding to the impulse elements of the sign combinations, separate control means for the individual contact elements, a common drive for said control means, and in cooperation withsaid transmitting arrangement an arrangement at the receiving end containing a contact device adapted to pass on the coded arriving impulses, an arrangement corresponding with the coding mechanism at the transmitting end for decoding the current combinations received, and a mechanism in a telegraph apparatus for the reception and translation of the decoded current combinations.
  • a transmitting arrangement which contains in combination a keyboard for setting electric impulse combinations of the signs to be transmitted, a coding mechanism adapted to change its setting during the transmission of the telegraph signs with means for interchanging the se quence of the successive dispatch of the impulses of the sign combinations set, an arrangement of contacts adapted to effect the dispatch of the impulse combination coded by the interchange of the impulse elements, and in cooperation with said transmitting arrangement an arrangement at the receiving end containing a contact device adapted to pass on the code-d arriving impulses,- an arrangement corresponding with the coding mechanism at the transmitting end for decoding the impulse combinations received, and a mechanism in a telegraph apparatus for the reception of the decoded impulse combinations.
  • a transmitting arrangement which contains in combination a keyboard for setting electric impulse combinations of the signs to be transmitted, a coding mechanism adapted to change its setting during the transmission of the telegraph signs with means for changing the character as Well as interchanging the sequence of the dispatch of the impulses of the sign combinations, an arrangement of contacts adapted to effect the dispatch of the coded sign impulse combinations, in cooperation with said transmitting arrangement an arrangement at the-receiving end containing a contact device adapted to pass on the coded arriving impulses, an arrangement corresponding with the coding mechanism at the transmitting end for decoding the impulse combinations received, and a mechanism in a telegraph apparatus for the reception of the decoded impulse combinations.
  • a transmitting arrangement which contains in combination selector bars adapted to be relatively shifted and dispatch the impulse combinations coded by the change of the character of the individual impulses.
  • a transmitting arrangement which contains in combination a contact arrangement adapted to set the sign impulse combinations consisting of a number of contacts corresponding with the impulse elements of the sign combinations,
  • a transmitting arrangement which contains in combination an arrangement for setting electric current combinations of the signs to be transmitted, a coding arrangement adapted to change its setting during the transmission of the signs, which consists of mechanically adjustable contact controlling means which code the set impulse combinations prior to their dispatch by changing the polarity of the individual impulses and by interchanging the sequence ofthe dispatch of the individual impulses, a
  • the circuit of the first impulse element of the original combination will now be traced: battery BA, upper contact 1 closed upper contact 10 connecting conductor l contact 4 of the set of contacts 1w, further closed contacts of the sets of contacts not shown of the arrangement OW, closed left-hand contact 1 of the contact set 6w, further contacts of OW, single transmitting contact 876 relay SR, battery midpoint MB.
  • the circuit for the fifth impulse element will in corresponding manner pass across the single transmitting contact sls, if the further circuits of the remaining impulse elements are tapped by tie transmitting contacts corre ponding with t em.
  • the transmitting process briefly 'takes place as follows: by depressing the key Te the selector bars 1 to 5 are shifted and in addition thereto the bar 6 is moved towards the right whereby the contactak is closed. A circuit is thus completed across the negative pole, contact ale, relay AR, positive pole, in which the starting relay AB is energized and reverses its contacts can and an. Across contact ar is then connected the coupling magnet AM, which disengages the lockin lever AKH. The pin S detained by the paw lever KH is then released whereby the coupling discs are coupled with each other.
  • the motor shaft MW drives the cam shaft SW.
  • the polarized transmitting relay S'R was energized across the negative pole and battery midpoint, so that the starting impulse is sent into the line.
  • the starting impulse is limited by the contact slc which is opened shortly after the start of the transmitting shaft SW.
  • the impulse combination transmitted by the contact'ar in the transmitter is at the receiving end taken up by the receiving relay OER of the decoding device (Fig. 2).
  • the coupling magnet AMF is ener ized by the reversal of the contact, so that t e startstop coupling .AFK couples the receiving shaft F with the continuously rotating motor shaft MW in the manner described before.
  • the contact els is opened by the advance of the cam F so that the circuit for the coupling magnet AMF is opened and the contact cerbecomes disengaged for the now following impulses.
  • DOW and DOT have accurately the same position as the contacts of the coding arrangement in 'the transmitter and remain stationary during the reception of an impulse combina-' tion.
  • the incoming impulses of the impulse combination are in succession distributed by the cams ela to 070,, over the individual connecting conductors Z, to 1,, which now lead the impulse values across the contacts of the coding arrangement DOW and across the contacts of the coding arrangement DOT, whereby the condensers O to O are correspondingly charged.
  • the impulse coming in first will thus pass across the contact 670 conductor Z across the contacts of the arrangement DOW not shown, the closed contact 1 of the set of contacts Gd'w, whereby it travels to the place of the fifth impulse and now passes on across the contacts dw not shown, the closed contact 2 of the set of contacts' Ida; and across the upper contact 5dt of the coding arrangement DOTto the lower plate of the condenser C
  • the upper plate of this condenser is across the lower closed contact of 5dt connected with the mid point MB of the battery so that in this circuit the condenser O is charged in the sense of the original sign element. In the same way the further condensers are charged by the subsequent impulses.
  • the relays set their contacts 0' to 7' correspondingly so that these contacts represent contact arrangement adapted to efiect the dispatch of the coded currentcombinations andin cooperation with the transmitting arrangement apparatus at the receiving end containing an arrangement which as regards setting and mode of operation corresponds with the coding arrangement of the transmitting end and embodies meansfor decoding the impulse combinations coded by changesinthepolarity of the impulses andby the interchange of the sequence of the dispatch of the impulses, and.
  • a transmitting arrangement which contains in combination an arrangement for setting electric current combinations of the signs to be transmitted, a coding mechanism adapted to change its setting during the transmission of signs, which consists of a plurality of cams connectspeeds and adjustable by mechanical and electromagnetic driving or coupling means,
  • a transmitting arrangement which contains in combination an arrangement for setting electric current combinations of the signs to be transmitted, a coding mechanism adapted to change its setting during the transmission of signs, which consists of a plurality of cams connected with one another at equal and at different speeds and adjustable by mechanical and electromagnetic driving or coupling means, which cams are provided with different projections orrecesses and by which contacts are controlled adapted to change the character of the impulses of a set combinaa contact arrangement for dispatching the coded combinations and in cooperation with the transmitting mechanism an arrangement at the receivingend which contains apparatus corresponding with the coding arrangement at the :transmitting end and contains,
  • a transmitting arrangement which contains in combination rrangement for setting electric current an co binations of the signs to be transmitted,
  • a coding arrangement adapted to change its setting during the transmission of signs
  • two shift contacts each assigned to the first impulses of the sign impulse combinations adapted to be controlled by cams
  • means for resetting the coding arrangement during the duration of the last impulse for the next sign combination a contact arrangement consisting of contacts adapted to be in succession operated by cams for tapping and dispatching the coded impulse combinations, and in cooperation with the transmitting arrangement an apparatus at the receiving end containing a contact arrangement adapted to transmit the coded impulses coming in, a mechanism for decoding the current combinations sent and corresponding with" the coding mechanism at the transmitting end, and apparatus for receiving the decoded current combinations.
  • a transmitting arrangement containing in combination an arrangement for setting electric combinations of the signs to be dispatched, an arrangement adapted to change its setting during the transmission ofthe signs to code the set electric current combinations, a contact arrangement adapted to effect the dispatch of the coded current combinations, and in cooperation with the transmitting arrangement an contacts adapted to be controlledby a card arrangement at the receiving end containing shaft, an electric register to whichare su'p- -plied decoded the coded impulse combinations, an arrangement consisting of such a I number of sets ofcontact springs each comas regards heginningand end, 'means'for controlling said spring sets; for the t correct de-I I ooding,'means consisting of two double: con- I a facts I each for setting the register as regards I I the character of the non-coded combinations,-
  • trio: current"combinations a contact arrange' I ment adapted to effect the dispatch I of the I I coded current combinations, and in coopera tion with the transmitting arrangement an I arrangement at the: receiving end containing a. contact arrangement fort-he retransmission I of theincoming coded impnlsecombinations 1 1 v v to a decoding mechanism corresponding with I the coding mechanism at the'transmitting end consisting of twoarrangements adapted to he controlled by cams, of whichone uncodcsthe I I scquence of the impulses, the other the polarity of the impulses of the sign comb nations, I I aregister-consisting of condensers; adapted to i I beset inthesense of the. decoded sign combinationsacross thedecodingmechanism, a
  • said cod- I ing mechanism including :a: plurality of contact elements corresponding to the impulse I 1 I I I elements'of the sign combinations,separatc i I control means'for the individual contact ole adapted to pass on the coded arriving int paratus forthe reception ofthe deco pulsecombinations; .I I. 1' o In testimony whereof we;
  • adapted to tap the contact of the polarized relays in succession and to transmit the sign combinations to the receiving magnet of the telegraph apparatus means for operating the contact arrangements during every transmission of a combination of signs, means for re- 7 setting the decoding mechanism during the transmission of the signs, means for advancing the cams difl'ering from one another through which the sets of springs of the dccoding mechanism are controlled by difierent amounts in correspondence with the trans mitting end, and means for operating simultaneously the contacts of the contact arrangement by which the register is tapped.
  • a transmitting arrangement which contains in combination a keyboard for setting electric impulse combi nations of the signs to be transmitted, at coding mechanism adapted to change its setting aflix: our signa- I-EBERHARD HETTLER.
  • a common drive'for ;said-c(mtrolp means, and: in: cooperation with said trans, mitting arrangement an arrangement :at the I 1 receiving end containingacontact 'devicc"" pulses, an arrangement; corresponding with 'the rcoding-mechanism at the transmittingend-for decoding the impulse'combinations i i received, and a mechanism 'in a telegraph' ap I I I dcd im- IZU

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Knitting Machines (AREA)
  • Lock And Its Accessories (AREA)
  • Transmission And Conversion Of Sensor Element Output (AREA)
  • Storage Device Security (AREA)
US551206A 1930-07-18 1931-07-16 Secret telegraph system Expired - Lifetime US1912983A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE615016T 1930-07-18

Publications (1)

Publication Number Publication Date
US1912983A true US1912983A (en) 1933-06-06

Family

ID=34812891

Family Applications (1)

Application Number Title Priority Date Filing Date
US551206A Expired - Lifetime US1912983A (en) 1930-07-18 1931-07-16 Secret telegraph system

Country Status (5)

Country Link
US (1) US1912983A (ru)
BE (1) BE381441A (ru)
DE (2) DE615016C (ru)
FR (1) FR721499A (ru)
GB (1) GB386676A (ru)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2458406A (en) * 1945-09-28 1949-01-04 Ibm Ciphering and checking device
US2629012A (en) * 1949-10-05 1953-02-17 Edgar Gretener Device for producing current impulse combinations
US2765364A (en) * 1950-10-05 1956-10-02 Hagelin Boris Caesar Wilhelm Keying mechanism
US2785224A (en) * 1952-08-19 1957-03-12 Edgar Gretener Enciphering device
US2789159A (en) * 1953-08-18 1957-04-16 Dreyse Richard Translating device for transmitting and receiving coded messages
US2797260A (en) * 1952-01-30 1957-06-25 Zenith Radio Corp Subscription television system
US4187393A (en) * 1955-08-23 1980-02-05 Deweese Eugene R Jr Key generator

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE767392C (de) * 1938-05-21 1952-07-31 Lorenz A G C Verfahren zur Erzeugung und Aussendung von verschluesselten Nachrichten nach dem Start-Stop-System der Fernschreibtechnik
DE767367C (de) * 1939-05-11 1952-06-19 Lorenz A G C Verschluesselungseinrichtung zur zeitlichen Vertauschung von Fuenfer-Alphabet-Impulsen
DE744693C (de) * 1941-04-26 1944-01-22 Opta Radio Ag Zeichengebereinrichtung mit einer Mehrzahl umlaufender als Zeichentraeger bei der Signalgabe dienender Nockenscheiben, die unmittelbar einen gemeinschaftlichen Geberkontakt steuern

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2458406A (en) * 1945-09-28 1949-01-04 Ibm Ciphering and checking device
US2629012A (en) * 1949-10-05 1953-02-17 Edgar Gretener Device for producing current impulse combinations
US2765364A (en) * 1950-10-05 1956-10-02 Hagelin Boris Caesar Wilhelm Keying mechanism
US2797260A (en) * 1952-01-30 1957-06-25 Zenith Radio Corp Subscription television system
US2785224A (en) * 1952-08-19 1957-03-12 Edgar Gretener Enciphering device
US2789159A (en) * 1953-08-18 1957-04-16 Dreyse Richard Translating device for transmitting and receiving coded messages
US4187393A (en) * 1955-08-23 1980-02-05 Deweese Eugene R Jr Key generator

Also Published As

Publication number Publication date
DE615016C (de) 1935-06-24
GB386676A (en) 1933-01-17
BE381441A (ru)
FR721499A (fr) 1932-03-03
DE666436C (de) 1938-10-21

Similar Documents

Publication Publication Date Title
US1310719A (en) Secret signaling system
US1912983A (en) Secret telegraph system
US1943475A (en) System for selective calling of telegraph stations
US2225657A (en) Telegraph message classification system
US2279353A (en) Telegraph system
US1864074A (en) Telegraph signaling system
US2406829A (en) Telegraph system
US2406023A (en) Teletypewriter signal enciphering system
US2495705A (en) Multiple frequency telegraph system
US2547515A (en) Secrecy system
US2523300A (en) Printer telegraph circuit
US1557633A (en) Translating device
US2981794A (en) Teleprinter secrecy system
US1686585A (en) Telegraph cipher system
US1356546A (en) Ciphering system
US1868967A (en) Secret telegraphy system
US2110149A (en) Code transmission system
US2504621A (en) Enciphering and deciphering device for secret telegraph systems
US2629012A (en) Device for producing current impulse combinations
US2458406A (en) Ciphering and checking device
US2353673A (en) Code signaling system
US1909838A (en) Telegraph exchange system
US2288645A (en) Posting system
GB632774A (en) Improvements in type printing telegraph systems
US2658943A (en) Printing telegraph system