Patent GB-632795-A (GB)
Title: Code-convertor
IPC: H03M5/00
Filed: 1946-08-21
Abstract: 632,795. Type-printing telegraphy. STAATSBEDRIJF DER POSTERIJEN TELEGRAFIE EN TELEFONIE. Aug. 21, 1946, No. 24969. Convention date, Nov. 19, 1941. [Class 40 (iii)] A telegraph circuit arrangement for translating from a five-unit code to a seven-unit equal-ratio code comprises means whereby the first five-unit element controls the application of a voltage to a single conductor, and the remaining four elements are divided into two pairs, each of which controls the application of voltages to a corresponding group of three conductors. The seven-unit code employed is an equal-ratio code comprising three marks (M) and four spaces (S), and each character is formed of a single first element followed by two groups of three elements each. The single element is produced by the first element of the five-unit code and, in general, a mark gives rise to a mark and a space to a space. The two three-unit groups are produced by the remaining two pairs of units of the five-unit code. The combinations SM, MS, SS, MM give rise respectively to the " normal " combinations SMS, MSS, SSM, SSS or the " reverse " combinations MSM, SMM, MMS, MMM. The first three five-unit combinations mentioned each contain a space and may be called space combinations, and the five-unit signals may be divided into five categories. When the five-unit signal begins with a mark and contains two space combinations the resulting seven-unit signal comprises a mark, a normal combination, and a second normal combination, producing the required three marks. B. When the five-unit signal begins with a space and contains two space combinations, the resulting seven-unit signal comprises a space, a normal combination, containing one mark, and a reverse combination containing two marks. C. When a five-unit signal begins with a mark and contains a space combination and a mark combination MM the seven-unit signal comprises a mark, the combination SSS and a reverse combination. D. When a fiveunit signal begins with a space and includes a mark combination and -a space combination, the first seven-unit element is a space, and the first three-unit group is SSS so it is impossible to produce more than one combination MMM for the last group. To overcome this difficulty a signal space, mark combination, space combination is arbitrarily arranged to give rise to space, reverse combination, and SMS while space, space combination, and mark combination gives rise to space, reverse combination, SSM. E. The signal S, MM, MM gives rise to a space, normal combination, reverse combination. The signal M, MM, MM gives rise to a space, reverse combination, normal combination. This latter is the only signal in which the polarity of the first element changes during translation. Circuit details. The five-unit combination is set up on contacts I ... V, Fig. 1, of which the upper position represents a mark. If the initial five-unit element is a space then contact I allows positive spacing battery to go to line 1. If the initial element is a mark, and all other elements are marks (case " E " above), contact I connects positive spacing battery to line 1. If one of the following elements is a space then one of the contacts II ... V will connect negative marking battery to line 1. The pair of elements set up on contacts II and III produce a " normal " combination on lines 3 ... 5 by the interaction of relays B and C, while the elements set up on contacts IV and V produce a " normal " combination on lines 5 ... 7 by the action of relays D and E. This arrangement takes care of case " A " above. In case " B " the first element is a space and relay A is operated so that over a2 up, and either d1 or e1 normal relay G operates. The contacts g2, g3 have the effect of reversing the polarity of the leads to which they are connected and so producing the necessary " reverse combination on lines 5 ... 7. In case " C " either both relays D and E operate to the combination MM and at d1, e1 operate relay F which at f1, f2 has the required effect of reversing the polarity produced on lines 1 ...3, or else relays B and C both operate to operate relay G, which reverses the last combination on lines 5 ... 7 at contacts g2, g3. In case " D," if relays A, B and C are energized i.e. the combination MM occurs early as in the letter c ; relay G is energized over both opposing windings and does not operate, but both relays F and H operate. At g2 and h3 the special combination SMS is set up on lines 5 ... 7. At f1 and h1 the combination determined by relays D and E at d2, e3, e4 is set up on lines 2...4. If relays A, D and E are energized (i.e. the combination MM occurs last, as in letter g) relay F will operate. Contacts g2 and g3 normally produce the special combination SSM on lines 5 ... 7 while contacts f1, f2 operated produce a normal combination on lines 2 ... 4 as determined by relays B and C. The operation of a relay S (not shown) produces at contacts s1 ... s3 a special warning signal SSMMMSS. A somewhat similar circuit arrangement (Fig. 3, not shown), ensures the re-translation at the receiver from seven to five-unit code. Specifications 519,633 and 632,774 are referred to.