ARRANGEMENT FOR CONTROLLING COMMUNICATION TERMINALS

Abstract: A data processing arrangement (10) comprises four standard VDU stations (13), each provided with its own identification LED (15), a single keyboard (11) and a control unit (17) connectable to the VDU stations (13) by cables (18) and to the keyboard (11) by a cable (20). The control unit (17) comprises switchable circuitry operable by a switch (19) connectable to the control unit (17) by a cable (21). Operation of the switch (19) enables the keyboard (11) to address an individual VDU station (13) for the presentation of data thereby, in the conventional manner.

Description: Arrangement for controlling communication terminals BACKGROUND TO THE INVENTION This invention relates to data processing arrangements, and is particularly concerned with control units therefor. In a main frame computer environment there are many situation where several computer VDU (Yisual Display Unit) terminals/screens (hereinafter VDU stations), each with their own keyboard, are controlled by a single operator. In normal operation and for obvious reasons only one VDU stat is written to at a time by the operator using a keyboard; the oth VDU stations are most possibly being used as a reference for information input. Under these conditions and where, for example, the operator is controlling four VDU stations, the keyboards will spend 75 of their life unused. Having this many keyboards controlled by one operator in itse causes problems such as entries made on the wrong keyboard and congestion of the work surface. It also represents a waste of capital and in some circumstances a security risk. ΞUMI1ARY OF THE INVENTION According to the invention, a control unit for a data process arrangement comprising a plurality of VDU stations, each provided its own identification means, and a single keyboard, the control unit being connectable to both the VDU stations and the single keyboard, and comprising switchable circuitry operable to enable the keyboard to address an individual VDU station for the presentation of data thereby. The switchable circuitry is preferably operable sequentially whereby, in the event of one VDU station not being addressable _*• for the presentation of data, the next available station in the sequence is caused to be so addressed. The switchable circuitry is also preferably operable to activate the individual identification means of the VDU stations in sequence. Active sensing override means may he provided which are operable to enable the keyboard to address a VDU station which otherwise would not be addressable by reason of the circuitry mentioned in the penultimate paragraph. The active sensing override means enable a switch to channels where a VDU station is powered down or disconnected. So as to provide substantial protection to both internal and external circuitry where necessary the circuit uses a combination of fuses current limiters and opto-isolators. In extreme cases a daughterboard PCB (Printed Circuit Board) may be plugged into the main PCB, offering further protection. The invention also comprises a data processing arrangement provided with the control unit. ADVANTAGES OF THE INVENTION With reference to the above example of one operator controlling four VDU stations, the present invention enables the elimination of three keyboards. Thus a substantial saving.in space is realised. Where once a desk was covered in keyboards, there need now be only one. Furthermore, the invention can result in less incorrect entries and improved efficiency. In addition, a significant cost saving may be made since fewer keyboards have to be purchased, and finally, security can be enhanced by the ability to disable data input to all VDU stations from one location. BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings, wherein:- Figure 1 is a synoptic diagram of a data processing arrangement which makes use of a control unit according to the invention, Figures 2A to 2G together provide a diagram of circuitry used in the control unit of Figure 1, and Figure J is a key to the complete diagram. DETAILED DESCRIPTION OF THE PREFERRED ΞIBODIMΞπT With reference to Figure 1, a data processing arrangement 10 comprises four standard VDU stations 13, each provided with its own identification means 15, a single keyboard 11 dedicated to the stations 13, and a control unit 17 connectable to the VDU stations 13 by port connecting cables 18 and to the keyboard 11 by a port connecting cable 20. Each of the VDU stations 13 is provided with a data input (not shown) connected to the back of each station. As will be apparent by the description that follows, the control unit 17 comprises switchable circuitry (Figures 2A to 2Cr) operable to ena.ble the keyboard 11 to address an individual VDU station 13 for the presentation of data thereby, in the conventional manner. The said circuitry, which is in the form of a printed circuit board, is manually switchable, by operation of a standard scroll switch 19. The switch 19 is connectable to the control unit 17 by a cable 21 and is mounted on the keyboard 11, so as to be readily accessible to the keyboard operator. Depression of the VDU station selection switch 19 is, as explained below, confirmed by an audible signal and highlighted by functioning of the identification means 15 of the selected station 13 as well as by one of a group of four light emitting diodes (LED) 22 mounted on a control panel 17a. of the control unit 17. The panel 17a , forms one end of the unit 17 and so is not fully visible in Figure 1. The panel 17a. also incorporates a key-operated security switch 24 for locking the keyboard 11 to a selected VDU station 1~ for disabling keyboard data flow. The key of the switch 24 is removable. The group of four LEDs 22 is shown in Figure 2E. The group is provided with supply and return connections 26, 27 respectively. (Figure 2F_). The panel 17a , carries two further LED's, namely 28, 29, also shovm in the right-hand side of Figure 2A. LED 28 is used to indicate when active sensing override (ASO) described below is in operation. LED 29 is used to indicate when power is being supplied to the control unit 17. The VDU station identification means 15 of this example comprise LED's connected to the control unit 17 by branches 18a. of the cables 1 The control unit 17 is provided with an electrical power input cable 23 connectable to a - 8 volt supply. In the example illustrated by Figure 1, each of the VDU stations is for the presentation of different data. For example, money exchang rates, commodity values, company share values etc. With further reference to Figures 2A etc., depression of the VDU station selection switch 19 takes pin 5 of IC 13 of the circuitry high. In addition pin 8 of IC 10 and pin 10 of IC 11 go high. IC 11 is a 451^ programmable up/down binary counter and is now set for counting up. One quarter of IC 10 and IC 13 are connected to form a XOR/AND set-reset latch (shown in detail on the right-hand side of Figure 2Cr). This is set assuming that IC 11 remains in the 'up' mode. Pin 4 of IC 13 also goes high taking with it, pins 4 and 12 on IC 9, pin 6 on ICs 5 and 6. (A low frequency oscillator line _ marked 'LF0' is also taken high but will be described later). The action of pin 6 on ICs 5 and 6 going high inhibits the flow of data through the circuit. IC 9 is a dual monostable wired for the leading edge, non- retriggerable mode. A high on pin 12 produces a positive logic pulse of user definable length on pin 10. This activates (Figure 2D) a tone generator 34 for a given period; it also connects to pin 6 on ICs 5 and 6. This is done in order to mask any contact bounce from the switch press. Pin 6 of IC 9 also provides a positive logic pulse of much shorter duration, although switch bounce slightly prolongs it, which passes out to take pin 15 of IC 7 high. This in turn disables the currently selected output of IC 7 (a default address) pin 12. Thus pin 12 goes low. As a result pin 1 of IC 10 also goes low. Pin 3 of IC 10 follows suit transmitting the more negative logic pulse to pin 15 of IC 11. Pin 15, IC 11 is held low until the pulse ends. IC 11 switches on the rising edge of a pulse so that its counter is incremented (up) by one only when the logic on pin 15 goes high. The output address on pins β and 11 of IC 11 can now change. These two pins now contain in the form of a binary code the newly selected port address. This code is used to directly switch the routing within ICs 5 and 6 via pins 10 and 9 of the same. At the same time IC 7 takes this binary code on pins 2 and 3 and converts it into a sequential code. That is, one of the putput pins on IC 7 (pins 4, 5, 6, 7) are taken high. This in turn does several tasks. Firstly it passes to IC 12 via a parallel resistor array on either pin 1, 2, 3 or 4 resulting in a suitable current being gated to one of the LED's 22 on panel 17a of the control unit 17, showing the selected address. Secondly it passes to one of the pins 1, 5, 8 and 12 on IC 17 where it causes the low frequency oscillator output to be switched to activate the correct identification LED 15 once again via the current gate, IC 12. y means of the selection sequence provided by the circuitry, the keyboard 11 is now connected to the correctly addressed VDU station 13 and the two units can function in the usual manner. The low frequency oscillator (LFO) is built around one sixth of IC 8 and is adjustable for frequency by the user. LFO output is a square wave which, to cut interconductor transients within the cables 18, is modified into a pseudo sine wave by simple resistor, capacitor filters on the outputs of IC 17. IC 17 also performs the task of isolating the LFO frequency control circuit from the RC filter although it results in four such filters being required. The LFO output line is held high by logic resulting from operation of switch 19. This overrides the LFO and ensures that when a new port/terminal is selected, the associated LED 15 comes on immediately and not after a complete LFO cycle. Once the switch 19 is released, the LED 15 flashes. Returning to the sequential output of IC 7 it is finally used to activate one half of the active sensing logic based around ICs 16, 14, 8 and 10. Each of the terminals connected and switched on supplies power to the keyboard 11. They do this through individual line fuses, and diodes being combined on a common bus connected to the keyboard 11. This bus is also fused. Before entering the diodes, each power bus is monitored by a combination of 1 mA current limiters and high sensitivity opto- isolators. Output from the isolators (IC 1, 2, 3> 4) is inverted by IC 8. The resulting logic levels are passed to IC 16 where a comparison is made with the newly selected address. If a terminal is connected, no change in the output state (high) of IC lβ occurs. However, if no_ terminal is connected at the selected address then the appropriate output pin (3, 4, 10 or 11) of IC 16 goes low. These output pins are connected to both halves of IC 14, a dual monostable configured for the trailing edge, non-retriggerable mode. If either of its control pins (5 or β) go low, i.e. no terminal, then a negative logic pulse of a preset length is produced on one of its output pins (7 or 9). These lines are combined at pins 5 and 6 of IC 10 whose output pin 4 follows their state. Thus, the negative going pulse is transferred to pin 4, IC 10. From here the pulse passes via switch 30 (Figure 2A - also referred to as switch one of the AS0 circuit) to pin 2 of IC 10 and from there, via pin 3» IC 10 to the clock input of IC 11 on pin 15. When the pulse ends the lines return high; pin 1 of IC 11 goes high causing a new address to be selected. To sum up, when no terminal was found to be connected at the selected port, a pulse was produced forcing the control unit 17 off that port and on to the next. It is by these means, when switch 19 is operated, the circuitry determines that a VDU station 13 is not addressable for the presentation of data by the keyboard 11. Consequently, the next available VDU station in the sequence provided by the circuitry is caused to be so addressed. This all occurs before a signal 'beep' has ended and as a result, before the inhibit on ICs 5 and 6 has been turned off. It follows that if switch 30 had been open circuit, no active sensing pulse could have passed through to IC 11 and the newly selected port would have been held regardless of the terminal state. Additional circuitry around switch 30 causes first an audible signal 'beep' and secondly a light to come on if it is open circuit. The audible signal 'beep' is provided by the tone generator 34 referred to above. Provision has been made to customise the important line states enabling a user to 'tie' them high or low using switches X or Y. (Upper right-hand corner of Figure 2E). Note that lines are only tied high to their respective terminal's power source. VDU screen input and output connections are identified by reference 45. (Figure 2JC). Some parts of the circuit have not been described. Such parts are mainly involved vάth sensing and reacting to different kinds of user switch. These are :- (a) a single scroll switch 19; ( ) a double up/down switch allowing the user to scroll forwards or backwards through the available terminals; (c) a quadruple switch to direct switching between terminals. Connections 3 > 36, 37> 38, 39, 40 are provided to accommodate the various forms of user switches. The single scroll switch 19 uses connections 35 and 37. A quadruple switch will use all six connections. (Figure 21? refers). With the up/down switch connect and the 'up' switch pressed, the circuit works as already detailed. With the 'down' switch pressed pins 1 and 2 of IC 13 go high resetting the output of the XOR/AND latch. This switches IC 11 to the count down mode via pin 10, IC 11, where it remains until an 'up' switch is used. If a quadruple switch is fitted, the protected (fuse one) line connected to pin 14 of IC 7 is taken high with the result that all pulses passing through it are diverted to pin 1 of IC 8. The pulses are "re-inverted" to positive logic and pass to pin 12 of IC 10. Providing a terminal is present at the selected port (and switched on) the pulse level passes to pin 1 of IC 11 where it transfers the code on pins 3, 4, 12 and 13 of IC 11- to output pins 6, 11, 14 and 2, of which only 6 and 11 are used. The code on input pins 3, 4, 12 and 13 depends upon which of the four buttons of the quadruple switch is pressed. A separate active sensing system is used in this mode and is based around IC 15 which simply compares the switch pressed with the port state. This determines whether or not a VDU station 13 is addressable for presentation of data by the keyboard 11, preventing selection if no terminal is present. Active sensing override is achieved (on operation of switch 30) by providing an easier route to ground for the current flowing from pin 11, IC 10 to pin 1, IC 11. This enables the keyboard 11 to address a VDU station which otherwise would not be addressable by reason of the circuitry. IC 13 also ensures that, regardless of which type of switch is actually fitted, an audible signal 'beep' is always generated (by way of IC 9 and tone generator 34) when the switch is operated. There are no unused gates in the circuit and so diodes and tie down resistors have been used to combine signals (where fast transients are not critical) in preference to using extea ICs. POSSIBLE IIODIFICATIONS OF THE IF7EUTI0N 1. Key code tra p -ping. Dedicated keycodes generated from the keyboard 11 may be used to initiate switching. This modification utilizes a keyboard keypress combination instead of a separate switch to change keyboard data routing, and could generate screen-displayed graphics to indicate screen selectio instead of the LED's 15. 2. Keyboard with integral ASI! (Active Switch lϋatrix) In this case the ASII would be part of an intelligent dedicated keyboard. 3. Data translating ASH This would translate data coding and rate where necessary to enable screens of different coding and rate to be accessed from a single keyboard whether with integral ASII or a separate arrangement.

Claims: C L A I M S 1. A control unit for a data processing arrangement comprising a plurality of VDU stations, characterised in that each VDU station (13) is provided with its own identification means (15), and a single keyboard (ll) is provided, the control unit (17) being connectable to both the VDU stations (13) and the single keyboard (ll), and comprising switchable circuitry operable (by 19) to enable the keyboard to address an individual VDU station for the presentation of data thereby. 2. A data processing arrangement as claimed in Claim 1, characterised in that the switchable circuitry is operable sequentiall whereby, in the event of one VDU station (13) not being addressable for the presentation of data, the next available station (13) in the sequence is caused to be so addressed. 3. A control unit as claimed in Claim 2, characterised in that the switchable circuitry is also operable to activate the individual identification means (15) of the VDU stations (13) in sequence. 4. A control unit as claimed in Claim 2, characterised in that it is provided with override means operable to enable the keyboard (ll) to address a VDU station (13) which otherwise would not be addressable by reason of the said circuitry. 5. A data processing arrangement, characterised in that it is provided with a control unit (17) as claimed in any one of Claims 1 to 4.

Inventors: GRUNDON KEITH RICHARD, GRUNDON MARK RICHARD, GRUNDON, KEITH, RICHARD, GRUNDON, MARK, RICHARD
Applicants: GRUNDON TECH LTD, GRUNDON TECHNOLOGIES LIMITED
Application year: 1988
Main classification: G06F3
IPC codes: G06F3