United States Patent: 3555186

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( 23795 of 23795 )

United States Patent	3,555,186
Allemann	January 12, 1971

KEY-OPERATED TELEPRINTER

Abstract

Key-operated teleprinter for the transmission of code symbols by the start-stop method, wherein each key triggers a further bit which has a first value and a second value for letters and numerals respectively, the bit combination and further bit being supplied to a reserve store adapted to store same and a master clock for controlling transmission of said bit combinations and associated further bits from the reserve store to the transmitter sotre, also for controlling the output circuit which transmits the bit combination to the transmission of a bit combination to said line if the further bit transmitted together with the bit combination is different from that transmitted with the preceding bit combination and means for producing an operating character for shifting the receiver from letters to numerals or vice versa.

Inventors:	Allemann; Adrian (Solevre, Welschenrohr, CH)
Assignee:	Hasler A. G. (Bern, CH)
Appl. No.:	04/724,150
Filed:	April 25, 1968

Foreign Application Priority Data


Apr 26, 1967 [CH]			5917/67

Current U.S. Class: 178/79 ; 178/17C; 341/22

Current International Class: H04L 25/40 (20060101); H04l 017/02 ()

Field of Search: 178/79,80,81,17,17A 340/345

References Cited [Referenced By]

U.S. Patent Documents


3162725	December 1964	Oleson
3296369	January 1967	Clark et al.

Primary Examiner: Claffy; Kathleen H.
Assistant Examiner: Jirauch; Charles W.

Claims

I claim:

1. A keyboard-operated teleprinter for the transmission of code symbols by the start-stop method, with a full keyboard, with an electronic transmitter store for storing the bits which form the code symbols and an output circuit for the successive transmission of the stored bits to a transmission line, wherein in addition to triggering the bit combination which represents the character, each key triggers a further bit which has a first value for all letters and a second value for all numerals, the said bit combination and the said further bit being supplied to a reserve store which is adapted to store at least one bit combination and the associated further bit, and a master clock which controls the transmission of the bit combination and of the associated further bit from the reserve store into the transmitter store and controls the output circuit for transmitting the bit combination from said transmitter store to the transmission line, and means adapted to temporarily block the transmission of a bit combination to the transmission line if the aforementioned further bit, transmitted together with the bit combination, has a value which is different from that of the further bit transmitted with the preceding bit combination and, depending on said different value, produces an operating character for shifting the receiver from letters to numerals or numerals to letters respectively, transmits said operating character to the transmission line and then releases the temporarily blocked transmission of the bit combination.

2. A teleprinter according to claim 1 having blocking means which blocks the aforementioned system when the bit combination corresponds to an operating character.

3. A teleprinter according to claim 1, wherein the reserve store is a register in which the first bit combination transmitted into the empty register and the further bit associated therewith is store in a register step disposed nearest to the output of the register.

4. A teleprinter according to claim 1 including a repeating system for the automatic and continuously repeated transmission of any desired character, triggered by depressing a repeat button wherein operation of the repeat button sets a flip-flop in a condition in which it blocks transmission of a bit combination and of the associated further bit from the reserve store into the transmitter store but not prior to the end of the transmission of a bit combination to the transmission line, furthermore causes the continuously repeated transmission of the bit combination stored in the transmitter store and is reset into its inoperative position after releasing the repeat button but not before the end of transmission of a bit combination to the transmission line, whereupon the continuously repeated transmission is terminated.

Description

The invention relates to a key-operated teleprinter for the transmission of code symbols by the start-stop method. These teleprinters operate in accordance with a code having five current steps, and in which each code symbol may have two meanings depending on whether it was preceded by a "letter" code symbol or by a "numerals" code symbol. One of these code symbols remains effective until the other is transmitted. Accordingly, the characters are divided into the group of letters and the group of numerals which also include the punctuation marks. The operating characters, for which the preceding transmission of "letters" or "numerals" is of no significance, belong to neither of the two groups. In most teleprinters shifting between the two groups is effected by depressing a correspondingly marked key; accordingly the keys may be designated simultaneously with a character of the letter group and the corresponding character of the numeral group.

Keyboards are also known with separate keys for each character of the two groups and are therefore referred to as full keyboards.

Teleprinter transmitters are also known with full keyboards which automatically effect shifting between the two groups by automatically transmitting the corresponding shift symbol if a key of one group is depressed after a key of another group has previously been depressed, but this procedure necessitates complicated mechanical means which require constant maintenance.

It is the object of the invention to replace the aforementioned complicated mechanical means by electronic means which occupy a small amount of space and can operate without maintenance and without wear.

According to the invention this aim is achieved in a key-operated teleprinter for the transmission of code symbols by the start-stop method and having a full keyboard, with an electronic transmitter store for storing the bits which form the code symbol and an output circuit for the successive transmission of the stored bits to a transmission line by a system wherein in addition to triggering the bit combination, which represents the character, each key triggers a further bit which has a first value for all letters and a second value for all numerals, the said bit combination and the said further bit being supplied to a reserve store which is adapted to store at least one bit combination and the associated further bit, and a master clock which controls the transmission of the bit combination and of the associated further bit from the reserve store into the transmitter store and controls the output circuit for transmitting the bit combination from said transmitter store to the transmission line, and means adapted to temporarily block the transmission of a bit combination to the transmission line if the aforementioned further bit, transmitted together with the bit combination, has a value which is different from that of the further bit transmitted with the preceding bit combination and, depending on said different value, produces an operating character for shifting the receiver from letters to numerals or numerals to letters respectively, transmits said operating character to the transmission line and then releases the temporarily blocked transmission of the bit combination.

An additional advantage achieved thereby is that the average keying speed is equal to the maximum transmission speed even in the event of irregular keying, individual characters being enabled to succeed each other at shorter intervals than those corresponding to the transmission time of one character.

An exemplified embodiment is described in detail hereinbelow by reference to the annexed drawing, in which:

FIGS. 1a--1g shows a summary of the circuit symbols employed to the extent to which they are not conventional;

FIG. 2 is a block circuit diagram of a key-operated teleprinter unit comprising a plurality of circuit elements being summarized by symbols illustrated in FIG. 1 and explained hereinbelow.

FIG. 1a shows an AND-gate, FIG. 1b an OR-gate and FIG. 1c an inverter. Inverters and gates can be combined in which case the input or output of the gate is marked with a dot; for example, FIG. 1d shows an AND-gate with a blocking input designated by a dot at the input. A plurality of gates can be combined in one symbol as indicated in FIG. 1e. FIG. 1f shows a shift register unit. The method of operation of this unit is explained by the adjacent circuit diagram. Said circuit diagram contains two flip-flops FF1 and FF2 each having two input gates and one inverter. The two positions which can be adopted by a flip-flop are designated with 1 and 0. A flip-flop will be in position 1 if the output at the designated side assumes the potential 1. The output of the undesignated side will then be at the potential 0. Application of a 1 potential to the input of the designated side sets the flip-flop to 1 while application of a 1 potential on the undesignated side sets it to 0. The unit is generally employed as a shift register when the inverted signal of a.sub.1 (a.sub.2 = a'.sub.1) is applied to the input a.sub.2. If the input t of the shift register unit changes to 1, the input gates of the circuit will be rendered conductive and FF1 is set to the position corresponding to the input a.sub.1. The second pair of gates is rendered conductive at the end of the t pulse and the position of FF1 and FF2 is transmitted. Both flip-flops can be set to 1 or 0 by means of the inputs s and r without reference to the inputs t and a.sub.1, a.sub.2. The unit may however also operate at a counter for the pulses t: if both inputs a.sub.1 and a.sub.2 are set to 1, FF1 will alter its position if t changes to 1 and will transmit this position to FF2 if t changes to 0.

The symbol of FIG. 1g refers to a simple flip-flop with two input gates and an inverter. If the clock input t changes to 1, the flip-flop will assume position 0 or 1 corresponding to the potential applied to the input a.

The teleprinter according to FIG. 2 comprises the following units separated from each other in the drawing by dot-dash lines: a master clock I, a keyboard mechanism II with seven contacts TO to T6, only one of the contacts T1 to T5 being illustrated in the interests of simplicity and being referenced with T1--5, an electronic reserve store III, an electronic transmitter store comprising a part IVa and a part IVb, a repeat system V, a shift system VI for shifting from letters to FIGS. and vice versa, an output circuit VII and blocking means VIII.

The master clock contains a single pulse transmitter IG which operates continuously and supplies a square-wave voltage b having an identical pulse and interval period and a frequency of 400 c.p.s. This frequency is divided into two by the shift register unit A. The output frequency is once again divided into two by the shift register B is no signal t.sub.0 is present. In this case the output of B will appear via the OR-gate OG on the input of a divider-by-8, comprising the shift registers D, E, F, but will be in operation only if M = 1. When the divider is inoperative, D, E and F will be set to 0. The outputs of the divider-by-8 control a decoder D1, having eight outputs t.sub.0--t.sub.7 of which the 1 potential is assumed by t.sub.0 when the counter is inoperative and successively by t.sub.1 to t.sub.7 when the counter is operative. If t.sub.0 = 0, B will be set to zero and the bypass via the AND-NOT-gate U1 will be rendered conductive so that the output frequency of A will appear at the input of the divider.

The symbols T0--T6 refer to the contacts of a keyboard mechanism. This mechanism has a full keyboard, that is to say a separate key is allocated to each letter, each numeral and each symbol. The contact TO is closed whenever a key is depressed, and further a combination of the contacts T1--T5 corresponding to the keyed character in the international telegraph code No. 2 and the contact T6 if the character is part of the numeral series of the aforementioned telegraph code. Coding is mechanical, and mechanical means prevent more than one key being simultaneously depressed.

Closing the contact TO sets an input pulse generator EG which delivers a delayed pulse whose minimum length is equal to at least 1 and whose maximum length is equal to at least 11/2 cycles of the pulse generator IG, and which begins with b', that is to say at the end of a b pulse. The beginning of the next b pulse causes the shift register A0 to be set and the pulse will appear at the output of A0 at the end of the b pulse. At the same time, the EG pulse will appear at the inputs of contacts T1--T6 and is transferred to the inputs of the associated shift registers A1--A6 to the extent to which the contacts are closed. The code symbol is recorded in the aforementioned shift registers when the aforementioned second b pulse occurs, is transferred to the shift registers B1--B6 when the third b pulse occurs and is transferred to the shift registers C1--C6 when the fourth b pulse occurs. The b pulses reach the control inputs of the shift registers via the AND-gates UA, UB, UC which are normally open. The numeral bit, corresponding to the position of the contact T6, is transferred through the shift register A0, B0, C0 in the same way as the letter bits so that the position of the numeral bits always corresponds to that of the letter bits. As soon as C0 changes to 1, the OR-gate OC, whose input is connected to the zero output of C0, will be blocked to prevent any further transmission from units B to units C. After the character is recorded, the output of EG will have returned to 0 so that 0 is recorded into the A steps of the shift registers when the third b pulse occurs while a 0 is recorded in the B steps for the fourth b pulse, the A steps remaining set to 0. As described in the following paragraph, transmission will be triggered as soon as 1 appears at the output of C0 but a second character, transmitted to steps A and B of the shift register in the manner already described can be stored prior to transmission. However, it remains stored in the B steps because the output of OB changes to 0 as soon as the outputs of B0 and C0 indicate that these units are set to 1.

A third character can be stored in the A steps of the shift registers in the same way whereupon the output of OA changes to zero thus blocking the AND-gate UA. Accordingly, a magnet MS mounted in the keyboard mechanism above the inverter IS, is thus operated to prevent any further key being depressed.

Experience has shown that the storing of three characters is sufficient in order to compensate for irregularities of keying even at very high typing speeds and with a readout speed of 50 baud, thus permitting teletyping at the maximum average speed. It is however possible without difficulty to increase the number of shift register steps.

When the shift register C0 is set, 1 will appear at the output of the OR-gate OM if it is assumed that the two other inputs of this gate, connected to the 1 outputs of the flip-flops S0 and W, are set to 0. The output of OM will in any case be set to 1 if this is not the case. As already described hereinbefore, the divider-by-8 DEF will run down and the pulses t.sub.1--t.sub.7 will be transmitted. Each of these pulses will have a duration of 20 ms. given a transmission speed of 50 baud.

In the inoperative condition the output t.sub.0 of the decoder D1 will be set to 1, accordingly this will also apply to the input t.sub.0 of the OR-gate OL, whose output is connected to the line L. Accordingly and in the inoperative condition the line will be continuously in condition 1, that is to say in a condition of continuous stop polarity. During the period t.sub.1 the output of OL changes to 0, that is to say to start. Two successive and nonoverlapping pulses t.sub.11 and t.sub.12 are formed during the period t.sub.1 by a combination of the signals b, A, B, A', B'. If the subsequently described flip-flop H = 0, the pulse t.sub.11 will trigger a signal Z at the output of the gate UZ, said signal effecting the transmission of the position of the shift registers C0--C6 to the flip-flops S0--S6. The Z-pulse passes via the AND-gate US6 for transmission from C6 to S6, said AND-gate being blocked by the output of the decoder D2 as described subsequently, but being rendered conductive for the transmission of letters and numerals. The signal Z also produces pulses at the outputs of the OR- gates OC and OB to shift the data in the reserve register by one step (from A to B, from B to C).

During the following periods t.sub.2--t.sub.6, the five AND-gates US1--US5 are successively rendered conductive by the pulses t.sub.2--t.sub.6, the positions of the five shift registers S1--S5 being thus scanned and being transmitted to the line via the OR-gate OL. In the aforementioned case the outputs of the gates UL2--UL6 will be set to 0. During the period t.sub.7, whose duration is also 20 ms., the input designated t.sub.7 of the gate OL is set to 1 to transmit the stop polarity to the line. During the first quarter of the period t.sub.7, S0 is set to 0; if no further character is to be transmitted, CO will be equal to 0, the output of OM will change to 0, the divider-by-8 DEF will then change into the inoperative position and remain there whereupon the transmission of the character is completed. If a further character awaits transmission the counter will continue to operate after a period t.sub.0 whose duration amounts to half of that of a normal step and will transmit the contents of the shift registers C0--C6 to S0--S6 during the period t.sub.1 as described hereinabove. In this case, the duration of the stop step will be equal to t.sub.7 + t.sub.0 = 11/2 step cycles.

By contrast to conventional teleprinters it is not necessary in the present teleprinter to depress the "letter (Bu)" or "numerals (Zi)" keys in order to obtain shift between letters or numerals. Since an individual key is allocated to each letter and each numeral, the latter also including the punctuation marks, depressing of the key alone determines which character is to be printed. Storing of a numeral bit in the reserve store also permits the differentiation. When the character is transmitted into the transmitter store, the numeral bit is stored in the flip-flop S6 and transmitted to the flip-flop K at the time t.sub.7. If the numeral bit has changed, K and S6 will be in different positions. If there was a change from numeral to letter, recording of 0 in S6 causes the output of the AND-gate UK1 to change to 1, since K was set to 1 by the preceding character. If the change takes place in the reverse direction, the positions of S6 and K will be interchanged and the output of UK0 will change to 1. In both cases, 1 will appear at the output of OK and will set the flip-flop H to 1 at the time t.sub.12. The output of the aforementioned flip-flop is connected to a blocking input of the AND-gates US1--US5 thus blocking the scanning of the shift registers S1--S5 by the gates US1--US5. Instead, a 1 will appear at the output of the gates UL2, UL3, UL5, UL6 during the periods t.sub.2, t.sub.3, t.sub.5, t.sub.6. If S = 1, that is to say if Zi is to be recorded, a 1 will appear during the period t.sub.4 at the output of the AND-gate UL4, so that the character Bu (11111) is transmitted; the output of UL4 = 0 during the period t.sub.4 for the character Zi so that the character Zi (11011) is transmitted.

The output signal of H blocks the zero position of S0 during the period t.sub.7, so that the output of OM remains at 1 and the counter continues to operate for a further cycle. During the same period t.sub.7 the flip-flop K is however reset since its preceding position differed from S6 and it is now set to the position of S6. At the time t.sub.12, H will be set to zero, since K and S6 assume the same positions. During the subsequent periods t.sub.2--t.sub.6 the signal contained in the store S1--S5 will be transmitted to the line.

The telegraph code No. 2 incorporates a few characters whose significance is unaffected by any preceding shift to letters or numerals. These are the operating symbols: ##SPC1##

Automatic transmission of letter or numeral characters should be blocked when these symbols are transmitted. To prevent such transmission, the changeover of the flip-flop S6 is blocked if an operating symbol appears in the shift registers C1--C5. To this end a decoder D2 is connected to the shift registers C1--C5 and is adapted to transmit an output signal if there is an operating signal other than Bu and Zi. The output of this decoder is connected to the blocking input of the AND-gate US6 and prevents the Z pulse from reversing the flip-flop S6. Accordingly, automatic transmission of a character is thus also prevented.

Reversal of S6 should not be prevented if one of the keys Bu or Zi is to be depressed, but automatic transmission of a further Bu or Zi symbol is to be prevented. Letter and numeral keys would not normally be required for the automatic transmission of characters, but they may be appropriate for certain functions, for example for signalling by repeated depressing of one or both keys. In order to prevent automatic transmission of Bu or Zi in such a case, the gates UK1 and UK2 are blocked for Bu or Zi by a signal transmitted by the decoder D2 so that the flip-flops S6 and K are set but not the flip-flop H which controls automatic transmission.

The same character can be repeatedly transmitted in a simple manner by simultaneous depressing of the letter or numeral key and of the repeat key T7. Depressing T7 sets the flip-flop W to 1, but only at the time t.sub.7. The keyed letter is therefore first transmitted as described above. After transmission of the character the flip-flop W changes to 1. The AND-gate UZ is therefore blocked and the transmission of the Z pulse and therefore the transmission of the next character from the store C to the store S1--S6 is blocked. At the same time the signal M appears continuously via the OR-gate OM at the input of the divider-by-8 DEF which circulates continuously and effects the continuous transmission of the characters stored in the store S1--S6. When the key T7 is released transmission of the current character is completed after which the flip-flop W is reset to 0 at the time t.sub.7, whereupon transmission of the character is terminated.

A simplified circuit was selected for the example. The expert will know that the same logic functions can be obtained in different ways and with different circuit elements. Moreover, the stores may be differently embodied, for example as magnetic stores, or they may be differently organized, the output store may function as shift register, the reserve store may operate in known manner as store with fixed data and floating input and output instead of operating as shift register with fixed input and output and floating data.

* * * * *

Current U.S. Class:	178/79 ; 178/17C; 341/22
Current International Class:	H04L 25/40 (20060101); H04l 017/02 ()
Field of Search:	178/79,80,81,17,17A 340/345