GB2149617A - Computer inter-communication apparatus - Google Patents

Abstract

Computer intercommunication apparatus which allows students provided with their own computers and VDUs to receive instruction from a master equipped with his own computer and VDU comprises a housing 10 having a control panel 11 and a set of sockets. The sockets 26-30 interconnect a master computer and an associated VDU with twelve student computers, and associated VDU's. The control panel includes two-way switches 13 associated with sockets 29 and 30, a two-way paging switch 16, a transmit/receive switch 20, and a twelve position selector switch 18. Circuitry enclosed in the housing includes a switch for connecting sockets 26 and 27, a set of switches for connecting socket 26 to respective sockets 30, a set of switches for connecting sockets 29 to sockets 30, and a set of switches for connecting sockets 29 to socket 27. <IMAGE>

Description

SPECIFICATION Computer inter-communication apparatus This invention relates to an apparatus for effecting controlled communication between a master computer and associated visual display unit (VDU) and a number of further computers or computer terminals and their associated VDU's.

A need for this type of apparatus arises where a number of students provided with their own computers and VDU's are receiving instruction from a master equipped with his own computer and VDU.

In such circumstances, the master may wish to demonstrate his programme to all the students or to an individual student and he may also wish to monitor the progress of students on an individual basis.

It is accordingly an object of this invention to provide a new or improved computer inter-communication apparatus capable of fulfilling this need.

According to one aspect of this invention there is provided a computer inter-communication apparatus comprising a first input for receiving a video signal from a master computer, a first output for transmitting a video signal to a display unit associated with said master computer, a set of further inputs each of which is arranged to receive a video signal from a respective further computer, a set of further outputs each of which is arranged to transmit a video signal to a further display unit associated with a respective one of said further computers, first switch means for connecting said first input to said first output, a first set of switch means each of which is arranged to connect said first input to a respective one of said further outputs, a second set of switch means each of which is arranged to connect a respective one of said further inputs to said first output, and a third set of switch means each of which is arranged to connect a respective one of said further inputs to respective one of said further outputs. Thus, the present invention provides an apparatus of simple construction which may be used by the master to transmit information from his computer directly to an individual student, to selected students, or to the class as a whole. Moreover, the master can use his VDU to monitor the progress of each individual student.

Because the apparatus of this invention is primarily a switching cicuit, it may be used to communicate between computers of differing types.

According to another aspect of this invention, there is provided a computer intercommunication apparatus which includes a circuit connectable to a master computer and an associated master visual display unit and having switch means operable for connecting two or more further computers or computer terminals and respective visual display units for effecting a selective communication between the master computer and its visual display unit and one or more of said further computers and respective visual display units as required.

This invention will now be described in more detail, by way of example, with reference to the drawings in which: Figure 1 is a face view of a control panel of an apparatus embodying this invention; Figure 2 is a rear view of the apparatus shown in Figure 1; Figure 3 is a block view of the apparatus connected to a master computer and associated VDU and also to a set of student computers and associated VDU's; Figures 4 to 9 together form a circuit diagram of the apparatus of Figure 1; and Figure 10 is a circuit diagram showing a modified form of the apparatus of Figure 1.

Referring now to Figure 1, the apparatus can be conveniently contained in a portable housing 10, the cover of which provides the control panel 11 which may be downwardly inclined forwardly for ease of use. The housing 10 is of robust metal construction to withstand hard usage and provide effective protection for the circuit components and the complete circuit is earthed to the metal housing.

The control panel 11 includes a set of twelve STUDENT switches 13, each of which may occupy a STUDENT WORKING position or a MASTER IN CONTROL position. The switches 13 are provided with a set of indicator lamps 14 and 15, each lamp 14 indicating that its associated switch is in the STUDENT WORKING position and each lamp 15 indicating that it is in the MASTER IN CONTROL position. The control panel 11 also includes a PAGING switch 16 which has an ON!position associated with an indicator lamp 17 and an OFFiposition associated with an indicator lamp 18. The panel 11 further includes a twelve position selector switch 18 and an associated 2 digit LED display 19 and a TRANSMIT/RECEIVE switch 20 which has a TRANSMIT position associated with an indicator lamp 21 and a RECEIVE position associated with an indicator lamp 22.

The panel also includes a main power supply indicator lamp 23, and positive/negative low voltage (5 volts) lamps 24 to indicate the supply of current to associated sections of the circuit.

As shown in Figure 2, the apparatus includes a jack plug 26 for connection to a master computer, a jack plug 27 for connection to its associated VDU, a pair of jack plugs 28 for connection to auxiliary VDU's, a set of jack plugs 29 for connection to student computers and a set of jack plugs 30 for connection to their associated VDU's. Also shown in Figure 2 is a mains input socket 31, a mains switch 32, and mains fuse access 33.

As shown in Figure 3, the apparatus 10 may be connected to a master computer 40 and its associated VDU 41, and to twelve student computers 42 and their associated VDU's 43.

As will be explained in more detail below, when the master wishes to transmit information from his computer 40 to some or all of the student VDU's 43, the STUDENT switch 13 for each VDU to which it is desired to transmit information is put in its MASTER IN CONTROL position and the PAGING switch 16 is put in its ON position. Also, if the master wishes to view the information on his VDU 41, the TRANSMIT/RECEIVE switch is put in the TRANSMIT position. Identical information generated by the computer will then appear on the master VDU 41 and on the student VDU's 43.

Each STUDENT switch 13 which is in the STU DENT WORKING position will cause information to be transmitted from the associated student 42 to the associated VDU 43.

In order to enable the master to observe the computer operation by a particular student as displayed on his VDU 43 without effecting the latters operation and, if desired, without his knowledge, the PAGING switch 16 is set to the OFF position, the selector switch 18 is moved to the position for the particular student, and the TRANSMIT/RECEIVE switch 20 is set to the RECEIVE position.

If the master wishes to transmit information to a particular student, the selector switch 18 is moved to the position for that student, the STUDENT switch 13 for that student is moved for the MAS TER IN CONTROL position, the PAGING switch 16 is moved to the OFF position, and the TRANSMIT RECEIVE switch 20 is moved to the TRANSMIT position. Identical information generated in the master computer 40 will then appear both on the master VDU 41 and the VDU 43 for the particular student.

As will be appreciated the manner in which the apparatus is used with the computers 40 and 41 and VDU's 42 and 43 can be varied according to requirements with student computers 41 and VDU's 43 selected or de-selected as appropriate and with observation of the work of any individual student and transmission of information thereto effected at will by the master. The varying rates at which information is absorbed by different students can be catered for by the apparatus and moreover the experience and self education of students by actual key operation of their computers 41 is made possible.

Where the master wishes to work alone, the TRANSIT/RECEIVE switch 20 is set to the TRANS MIT position. This enables the master to operate the master computer 40 with the display on the master VDU 41. In order to prevent interference with operation of the student computer 42 and VDU's 43, the PAGING switch 16 is moved to the OFF position. Also, the STUDENT switch 13 for the student presently selected by the selector switch 18 should be in the STUDENT WORKING position to prevent information being transmitted from the master computer 40 to the associated VDU 43.

Although not shown in Figure 3, one or two auxiliary VDU's may be plugged into the apparatus by using the sockets 28 thereby providing a display for all students.

Referring now to Figure 4 there is shown the power supply circuit for the apparatus. The cicuit includes rails L and N for connection to the mains voltage supply rails and a rail E for connection to the mains earth lines. The rails L and N are assocated with the mains switch 32 and the mains fuse 50 and mains indicator lamp 23 and these two rails are connected to a pair of 240V:12V transformers 51 and 52. The output of transformer 51 is connected to the + 12V and 0V supply rails. The output of both transformers is also connected to a voltage regulator 53 the output of which is connected to a +5V supply rail, a 0V supply rail and a -5V supply rail and these rails are also connected to the indicator lamps 24.

Referring now to Figure 5, there is shown a part of the circuit associated with the socket 26 for connection to the master computer 40. The socket 26 is connected through a pair of capacitors Cl and C2 to the base of a transistor TI which together with associated resistors operates as an amplifier. The amplified output signal being supplied to a rail 60.

The socket 26 is also connected through a further pair of capacitors C3 and C4 to the base of a transistor T2 which together with associted resistors also functions as an amplifier and provides an amplified signal on a rail TX. As will be explained in more detail with reference to Figure 9, the circuit includes twelve identical sub-sections each of which is associated with a pair of sockets 29 and 30. The rail TX is divided into twelve further rails TXI to TX12 each of which is connected to one of these sub-sections. The circuit of Figure 5 also includes twelve rails RXI to RX12 each of which is connected to one of these twelve sub-section and the rails RXI to RX12 are drawn into a single rail RX.The rail RX is connected through a pair of capacitors C5 and C6 to the base of a transistor T3 which together with associated resistors functions as an amplifier providing an amplified signal on a rail 61.

Referring now to Figure 6, there is shown the part of the circuit which is associated with the TRANSMIT/RECEIVE switch 20. The switch 20 comprises a pair of ganged double throw switches 20a and 20b. The pole of switch 20a is connected to the OV rail and one of the output contacts of the switch is connected through indicator lamp 22 to the +5V rail. The other output contact is connected through the lamp 21 to the +5V rail and also to a rail TR. The rail TR divides into twelve further rails TRI to TR12 each of which is connected to one of the 12 identical sub-sections mentioned above. The pole of switch 20b is connected to the socket 27 for connection to the master VDU 41, one of the output contacts of this switch is connected to rail 61 and the other output contact is connected to rail 60. The TRANSMITIRECEIVE switch 20 is shown in Figure 6 in the TRANSMIT position.

Referring now to Figure 7, there is shown the part of the circuit which is associated with the PAGING switch 16. The PAGING switch 16 comprises a pair of double throw switches 16a and 16b. The pole of switch 16a is connected to the OV rail and one of its output contacts is connected to a rail PG. The rail PG is divided into twelve further rails PGI to PG12, each of which is associated with one of the twelve identical sub-sections mentioned above. The pole switch 16b is connected to the OV rail, one of its output contacts is connected through lamp 17 to the +12V rail and the other output contact is connected through lamp 18 to the +12V rail. The switch 16 is illustrated in the ON position.

Referring now to Figure 8 there is shown a part of the circuit associated with the selector switch 18. The input of switch 18 is connected to the 0V rail and the switch has twelve outputs which are connected to rails CSI to CS12 each of which is connected to one of the twelve individual sub-sections mentioned above. The rails CSI and CS2 are connected to the cathodes of a pair of diodes Dl and D2, the anodes of which are connected to two inputs of a type 74147 decimal to BCD converter 70. Rails CS3 to CS9 are connected to the remain ing inputs of converter 70. The output of converter 70 is connected through four inverters 71 to the in puts of a type 7447 LED driver 72. The outputs of driver 72 are connected through a set of resistors 73 to the individual segments of a 7 segment LED display device 74.The outputs of inverter 71 are also connected to a set of rails BI, B2, 84 and 88 and these rails may be connected to the circuit which will be described with reference to Figure 10. Rails CSII and CS12 are connected to the cath odes of a pair of diodes D3 and D4, the anodes of which are connected to the anodes of diodes Dl, D2. Rail CS10, CSII and CS12 are also connected through three diodes D5 and a resistor RI to two segments of an LED display device 75. The devices 74 and 75 together provide the display 19.

Referring now to Figure 9, there is shown one of the twelve identical sub-sections mentioned above and, specifically, there is shown the sub-section which is connected to rails RXI, TXI, TRI, PGI, and CSI. This circuit also includes one of the STUDENT switches 13 together with its associated indicator lamps 14 and 15 and also associated sockets 29 and 30.

As may be observed in Figure 9, the switch 13 in fact comprises two ganged double throw switches 13a and 13b. In Figure 9, the switch 13 is shown in the MASTER IN CONTROL position. The switch 13a is associated with the indicator lamps 14 and 15.

The pole of switch 13b is connected through a diode D6 to one input of a NAND gate 80 and directly to its other input. The output of NAND gate 80 is connected to one input of a further NAND gate 81 the output of which is connected through an inverter 82 to the control terminal of an analogue switch 83. One of the contacts of switch 13b is connected to the two inputs of a NAND gate 84, the output of which is connected to the other input of NAND gate 81 and through an inverter 85 to the control terminal of an analogue switch 86. This contact of switch 13b is also connected through a resistor R2 to the 5V rail and the 5V rail is connected through a further resistor R3 and an inverter 87 to the control terminal of an analogue switch 88.The input of inverter 87 is also connected to rail CSI and rail CSI is connected to a further rail 89 which may be connected to the circuit shown in Figure 10. This one contact of switch 13b is also connected to a rail 90 which may also be connected to the circuit shown in Figure 10. The rail CSI is also connected through a pair of resistors R4 and R5 to the 0V rail and a junction of these resistors is connected to the base of a transistor T4, the collector of which is connected to one input of a NAND gate 91.

The collector of transistor T4 is also connected through a resistor R6 to the +5V rail. The other in put of NAND gate 91 is connected to rail TRI and also through a resistor R7 to the +5V rail. The out put of NAND gate 91 is connected through a diode D7 to the pole of switch 13b.

The rail RXI is connected through analogue switch 88 to a rail 93 and rail 93 is connected to the socket 29 for connection to the associated stu dent computer 42. Rail 93 is connected through an alogue switch 86 to a rail 94 and rail 94 is connected to the base of a transistor T5 which to gether with associated resistors functions as an amplifier and provides an amplified signal at its emitter. The emitter of transistor T5 is connected to the socket 30 for connection to the associated student VDU 43. The rail 94 is also connected through analogue switch 83 to rail TXI.

The operation of the apparatus will now be de scribed will now be described with particular refer ence to the individual sub-section shown in Figure 9. This sub-section will be referred to as sub-section 1.

As explained above, when the master desires to transmit information from his computer 40 to the student VDU's 43, the student switches 13 are set to their MASTER IN CONTROL positions and the PAGING switch is set ON.

With the switches in these positions, the outputs of NAND gates 80 and 84 are low (0V) thereby closing s$itch 83 and opening switch 86. Consequently, the video signal from the master computer 40 is connected through switch 83 and supplied as an amplified signal to the socket which is connected to the VDU 43 associated with section 1. If a master wishes to view the information on his VDU 41, the TRANSMIT/RECEIVE switch is set to the TRANSMIT position and so the video signal from the computer 40 is supplied via the rail 60 and switch 20b to the socket 27 which is connected to VDU 41.

If a master wishes to monitor the student associated with sub-section 1, the student switch 13 for section 1 is set to the student working position, the PAGING switch 16 is set to the OFF position the TRANSMIT/RECEIVE switch is set to the RECEIVE position, and the selector switch 18 is set to position 1. Consequently, switch 88 is closed thereby connecting the video signal from the associated computer 42 to rail RXI with result that the signal is amplified and connected via rail 61 and switch 20b to socket 27 and thereby supplied to VDU 41.

Also, a high signal (+5V) will be supplied to the two inputs of NAND gate 84 thereby closing analogue switch 86 with the result that the video signal output from the associated computer 42 will be supplied to the associated VDU 43.

If a master wishes to transmit information from his computer 40 to the VDU 43 associated with section 1, the appropriate student switch 13 is set to the MASTER IN CONTROL position, the TRANS MIT/RECEIVE switch is set to the TRANSMIT position, the selector switch 18 is set to the position for sub-section 1, and the paging switch is set off.

Consequently, rail TRI goes high thereby providing a high signal to one input of a NAND gate 91 and rail CSI is low thereby providing a high signal to the other input of NAND gate 91.

Consequently, the output of NAND gate 91 goes low and so a low signal is supplied to both inputs of NAND gate 80 and to both inputs of NAND gate 84. This will cause switch 83 to be closed and switch 86 to open with the result that the video signal from computer is supplied to the VDU 43 associated with sub-section 1.

Also, because the TRANSMIT/RECEIVE switch is in the TRANSMIT position, the video signal for master computer 40 will also be supplied to the master VDU 41.

The apparatus as described above is suitable for use with a composite video signal as such a video signal is transmitted over a single transmission line. Video signals are sometimes transmitted over a a set of parallel transmission lines, each transmission line being used to transmit a particular component of the signal.

For example, a black and white signal may be transmitted as four separate components, namely, the vertical synchronisation (VS) signal, the horizontal synchronisation (HS) signal, the intensity signal and the video signal. A colour signal may be transmitted as six separate components, namely, the vertical synchronisation signal, the horizontal synchronisation signal, the intensity signal, the red signal (R), the blue signal (B), at the green signal (G). Such signals can be transmitted an analague signals or as two state signals. Two stage signals are used, for example, to ensure the signals compatible with TTL circuitry.

The apparatus described above can be adapted to transmit either the four components, black and white signal or the six component colour signal in a form which is compatible with TTL circuitry by inclusion of the circuit shown in Figure 10. The apparatus of Fig. 10 uses seven rails to transmit the video signal and these rails can be used either to transit the four components of a black and white signal or the six components of the colour signal.

As may be appreciated, these modifications can be made by the addition of a single circuit board.

Figure 10 shows a circuit which is suitable for use with 6 student computers 42 and associated VDU's 43. In Figure 10, the part of the circuit enclosed by the dashed line 100 is associated with sub-section 1 of Figure 9 and it is to be appreciated that this section is repeated five times for the remaining five sub-sections. If desired, the circuit of Figure 10 could be expanded to handle all twelve student computers 42 and associated VDU's 43.

The circuit of Figure 10 includes sevel rails 101 to 107 which are connected to a seven port socket for receiving the video signal from the master computer 42. These rails are connected through two sets of inverters 108 and 109, the outputs of inverters 109 are connected to a seven line bus 110. The individual lines of bus 110 are connected to respective inputs of seven Texas Instruments type 74150N multiplexers 111. The output of each multiplexer 111 is connected to one input of a respective EXCLUSIVE OR gate 112, and the outputs of OR gates 112 are connected to a set of rails 121 to 127. The rails 121 to 127 are connected to a seven port socket for connection to the master VDU 41. The other inputs of OR gates 112 are connected to the rail TR of Figure 6.

The rail TR is also connected to the input of an inverter 129, the output of which is connected to one input of each of four NAND gates 130. The rails Bl, B2, B4 and B8 of Figure 8 are connected to the other inputs of NAND gates 130. The outputs of NAND gates 130 are connected to a four line bus 131 which is connected to the control inputs of multiplexers 111.

The video signal from the computer 42 associated with sub-section 1 is connected to a seven line bus 135 and each line of bus 135 is connected to one input of a respective NAND gate 136 and also to one input of a respective NAND gate 137.

Rail 89 from Figure 9 is connected through an inverter 138 to the other inputs of NAND gates 136.

The output of each of NAND gates 136 is connected to one input of respective one of multiplexers 111. Rail 90 of Figure 9 is connected to the other inputs of NAND gates 137 and the output of each of NAND gates 137 is connected to one input of a respective NAND gate 139. Rail 90 is also connected through an inverter 140 to one input of each of set of NAND gates 141. The other inputs of NAND gates 141 are connected to respective ones of the seven lines bus 110 and the outputs of NAND gates 141 are each connected to the other input of an associated one of NAND gates 139.

The outputs of NAND gates 139 are connected to a seven line bus 143 which is connected to a seven port socket for connection to the VDU 33 associated with sub-section 1.

When the master wishes to transmit information from his computer 40 to the student VDU's 43, the TRANSMIT/RECEIVE switch is set to the TRANSMIT position and the student switches are set to the MASTER IN CONTROL positions,and the PAGING switch is set to the ON position.

Consequently, the video signal on rails 101 to 107 is transmitted via inverters 108, 109, bus 110, multiplexers 111 and OR gates 112 to rails 121 to 127.

This video signal is also transmitted via bus 110 and NAND gates 141 and 139 to bus 143.

When the master wis to observe operation of computer 42 associated with sub-section 1, he sets the selector switch 18 to the position for sub-section 1, the STUDENT switch for sub-section 1 to the STUDENT IN CONTROL position, the TRANS MIT/RECEIVE switch to the RECEIVE position and the PAGING switch 16 to the OFF position. Consequently, the video signal on bus 135 from the computer 42, for sub-section 1 is transmitted via NAND gates 136, multiplexers 111, and OR gates 112 to rails 121 to 127 which are connected to the master VDU 41 and also via NAND gates 137 and 139 to bus 143 which is connected to the student VDU 42.

If the master wishes to transmit information from his computer 40 to the VDU 43 associated with Section 1, the appropriate student switch 13 is set to the MASTER IN CONTROL position, the TRANSMIT/RECEIVE switch is set to the TRANSMIT position, the selector switch 18 is set to the position for sub-section 1, and the PAGING SWITCH is set off. Consequently, the video signal on rails 101 to 107 is transmitted via inverters 108,109, bus 110, multiplexer 111 and OR gates 112 to rails 121 to 127 and also via bus 110 and NAND gates 141 and 139 to bus 143.

In Fig. 10, the NAND gates 136 are provided to reduce cross-talk and signal loss arising from self capacitance, inductions and radiation associated with the transmission lines between bus 135 and multiplexers 111. The EXCLUSIVE OR gate 112 act as buffers when the signal on rail TR is low and as inverters when this signal is high and ensure that the signals on lines 121 to 127 have the correct polarity.

It will be observed that the operation of the apparatus with the modification of Figure 10 is generally similar to the operation of the apparatus without his modification. It may also be observed that NAND gates 137, 139, 141 perform the same function as switches 83 and 86 of Figure 9 and that multiplexer 111 performs the same function as switches 88 and switch 20b.

The apparatus described above enables several student computers and associated VDU's to be interconnected with a single master computer and associated VDU without recourse to a network system and without the need for any additional software. Furthermore, the normal operation of the master and student computers and assocated VDU's are not affected in any way.

The apparatus thus provides a useful aid in the use of computers and VDU's for educational and demonstration purposes as well as for other uses of a similar nature.

If further practical application of the apparatus is for the selective control of television cameras, for example, in a security system in relation to a master display or monitor screen.

Claims (8)

1. A computer intercommunication apparatus comprising a first input for receiving a video signal from a master computer, a first output for transmitting a video signal to a display unit associated with said master computer, a set of further inputs each of which is arranged to receive a video signal from a respective further computer, a set of further outputs each of which is arranged to transmit a video signal to a further display unit associated with a respective one of said further computers, first switch means for connecting said first input to said first output, a first set of switch means each of which is arranged to connect said first input to a respective one of said further outputs, a second set of switch means each of which is arranged to connect a respective one of said further inputs to said first output, and a third set of switch means each of which is arranged to connect a respective one of said further inputs to a respective one of said further outputs.

2. An apparatus as claimed in claim 1, further including a set of operating switches and control means responsive to the operating switches for controlling said first switch means, and said first, second, and third sets of switch means.

3. An apparatus as claimed in claim 2, in which the operating switches include a transmit/receive switch having a transmit position and a receive position, a selector switch for selecting a desired one of said further inputs and the associated further output, a set of further switches each of which is associated with one of said further inputs and the associated further output, and in which the control means is arranged so that when the transmit/receive switch is in its transmit position the first input is connected to the first output and when this switch is in the receive position the selected further input is connected to the first output, and so that when one of said further switches is in its first position the associated further input is connected to the associated further output and when one of said further switches is in its second position the first input may be connected to the associated further output.

4. An apparatus as claimed in claim 3, further including a paging switch having an on position and an off position and in which the control means is arranged so that when one of said further switches is in its second position the first input is connected to the associated further output if either the paging switch is in its on position or said further output is the one selected by the selector switch.

5. An apparatus as claimed in any one of the preceding claims in which each video signal is a composite video signal transmitted over a single transmission line and each switch means is associated with a single transmission line.

6. An apparatus as claimed in any one of claims 1 to 3 in which each video signal comprises a set of individual signals transmitted over a corresponding set of parallel transmission lines and each switch means is associated with a set of parallel transmission lines.

7. An apparatus as claimed in claim 6, in which said first switch means and said second set of switch means together are formed as a set of multiplexers each of which corresponds to one of said individual signals.

8. A computer intercommunication apparatus including a circuit connected to a master computer and an associated visual display unit and having switch means operable for connection to one or more further computers or computer terminals and respective visual display units for effecting selective communication between the master computer and its visual display unit and one or more of said further computers and respective visual display units as required.