US 3612765 A
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United States Patent  Inventor Roger William Dawson 3,457,368 7/1969 Houcke 178/17 Brighton, Sussex, England 3,456,077 7/1969 Jones 178/ 17 ] Appl. No. 828,502 3,296,370 l/l967 Clark etal. l78/l7  Ffled May 1969 Primary Examiner-Kathleen H. Claffy  Patented Oct. 12, 1971 Assistant Examiner-Tom O Amico  Assignee Creed & Company B Attorneys-C. Cornell Remsen, Jr., Walter J. Baum, Paul W.
righton, Sussex, England H emminger, Percy P. Lantzy, Philip M. Bolton, Isidore  Priority May 30, 1968 T t d Ch I L J h  Great Britain ogu an at es 0 [31 25896/68  KEYBOARD LOGIC SYSTEM 1 Cl 2 D F rawmg ABSTRACT: A keyboard logic system for controlling  U.S. Cl 178/17 R, k b d l ki nd th transmitting time base for all operat- 340/365 ing conditions which includes a trip switch, operated by the f Cl H04] 15/12 actuation of any key, and two bistables. The first bistable is set  Fleld 0 Search 178/17, 17 when no keys are de ressed and the econd bistable is et 17 235/145; 340/365 when both the first bistable is set and the trip switch is 56 R i d operated. The second bistable serves to lock the actuated key 1 e ""Z N and release the time base. Further means are provided to UNITED STATES PATENTS release the time base at the instant when both the.runout 3,466,647 9/1969 Guzak l78/l 7 switch and the trip switch are actuated concurrently.
LOGIC] KEYBOARD TRANS- MITTER LINE TRANS- Inventor ROGER M DAM/s0 A Home y I as For column I as For coliumn as For column 5 9312 E? m I! SHEET 2 HF 2 OPERATING SEQUEBCES as For col umn KEY RISES KEY HELD DOWN KEY HELD nowu KEY HELD DOWN CHARACTER KE DESCENDS T MEBASE EMI TIMEBASE IEMITIS PULSE P] f or col umn 8M m w R 0M Kw Y m mil- K o m .Qlu s Al fim H TIMUOKR 5 E L C L NN 00 on 00 W00 o o In t e V3 C5 ae E an Y u mm.
KEY HELD DOWN PATENTEDUET 12 I97! Y RISES oes o I reaches P 0 088m T lincla mas J 1065 to O gago rd dhIocKs I Ke oiiard locKs 1 KEYBOARD Locic SYSTEM BACKGROUND ON THE INVENTION This invention relates to a keyboard transmitter for a teleprinter or the like.
"It is common for keyboard operators to proceed either at speeds less than the keyboard cadence speed or faster than cadence speed, and perhaps alternate between these rates. Also, key depression may vary between staccato and legato. These variations in mode of operation give rise to several different logical conditions in which correspondingly different logical decisions are necessary.
There are six keyboard conditions which a teleprinter trip logic must cater for.
a. A key is depressed and allowed to rise before the end of the resultant logic cycle.
b. A key is depressed and held down until after the end of the resultant logic cycle.
c. A key is depressed, allowed to rise then is depressed again before the logic cycle resulting from the first depression has finished.
cl. A key is depressed and the runout button is depressed before the end of the resultant logic cycle and held down.
e. A key is depressed and held down and after the end of the resultant logic cycle the runout button is depressed and held down.
f. The runout button is depressed and held down and then a key is depressed and held down.
Under conditions (a) and (b) the logic must clamp the time base at the end of the logic cycle.
Under condition (c) the time base must not clamp at the end of the logic cycle, but must continue to run so as to deal with the second key depression.
Under condition (d) the time base must remain unclamped until either the key or runout button is released.
Under condition (e) the time base must clamp at the end of the resultant logic cycle and release when the runout button is depressed and stay released until either the runout button or the key is released.
Under condition (f) the time base must remain clamped until the key is depressed and then must remain unclamped until either the key or the runout button is released.
SUMMARY OF THE INVENTION According to the present invention there is provided a keyboard transmitter having a trip-switch operated by the depression of any key, a time base for determining the timing of code signals emitted and locking means for ensuring that a depressed key is retained .in the depressed position for a predetermined time, a first bistable device which is set when no keys are depressed, a second bistable device which is set when said first bistable device is set and the trip-switch is operated, a first means connecting said second bistable device and the locking means such that when said second bistable device is set the locking means is conditioned to lock the depressed key down, second means connecting said second bistable device and the time base such that at the instant said device is set the time base is unclamped, a connection between the time base and said first bistable device such that a signal from the time base can reset the bistable device, a connection between the time base and said second bistable device such that a signal from the time base can reset the bistable device.
BRIEF DESCRIPTION or THE DRAWINGS An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:
F IG. 1 is a keyboard locking and timebase control logic circuit; and
F IG. 2 is a table setting out the logical sequence of events in the circuit of FIG. 1 for the possible operating conditions of the keyboard.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a trip contact TC and locking electromagnet EM form part of a keyboard of a teleprinter whose signalling timebase TB is clamped by the application of a logic 1 signal to path n and released when path m is at logic 0 level.
The trip contact TC has its pole connected to a logic I level, and is normally in its SB position, and a runout switch RS is normally open but closes to apply the logic 1 level to path h when the runout key is depressed.
The timebase TB provides several timing pulses for signal transmission, but also provides brief logic 1 pulses over paths s and e at instants at the beginning and the middle of the logic cycle respectively. Also, the timebase TB holds path j in logic 1 state during standby.
A bistable device 8, is set when contact TC is in its position SB and is capable of being reset shortly after by timebase output pulse P, over path 5. Bistable B, is normally held in it's set state by contact TC, but when TC moves to position TP subsequent events cause a pulse from P, shortly afterwards to reset 8,.
A bistable device B is set when a gate G, delivers an output and is reset by timebase output pulse P over path e. The gate G, serves to set the bistable device B when the device B, is set and contact TC arrives at its position TP.
A gate G together with an inverter l serves to combine signals from the runout and trip switches in such a way that the timebase TB cannot be clamped if both switches are operated.
A gate G serves to combine signals from the device B, and the timebase in such a way as to ensure that the timebase is reclamped at the predetermined time.
A gate G, serves as a point of confluence of information from the gates G and G The standby condition of the circuit is as follows:
Switch TC is at SB, path .r is at 0, path e is at 0, and path] is at 1.
Key RS is open. Therefore path a is at l and c is at l b is at 0 d is at 0 because b is at 0 f is at 0) and because a was at l g is at I) after A was at h is at 0 k is at 0) and because h is at 0 w is at l) m is at I because both 5 andj are at l n is at I because m and w are both at l.
The timebase is clamped because n is at l. The keyboard is unlocked becausefis at 0.
The six distinct sequences corresponding to the six keyboard operating conditions defined previously are set out in H6. 2 of the accompanying drawing, which is self explanatory.
It is to be understood that the foregoing description of specific examples of this invention is not to be considered as a limitation of its scope.
l. A keyboard transmitter comprising a trip switch actuated by the depression of any key, a time base, which is clamped in the normal state, for determining the timing of code signals emitted, locking means providing for the retention of a depressed key in the depressed position for a predetermined time, a first bistable device, coupled to said trip switch said first bistable device being set when no keys are depressed, a second bistable device operatively coupled to said first bistable device such that said second bistable device is set when said first bistable device is set and said trip switch is actuated, said second bistable device being further operatively coupled to said locking means and to said time base, such that when said second bistable device is set said locking means is conditioned to lock the depressed key down for said predetermined time and said time base is unclamped, said time base being switch and said time base such that whenever said trip switch and said runout switch are both actuated concurrently said time base will be unclamped to execute contiguous timing cycles until either the runout switch or the trip switch ceases to be operated.