IE872460L - A video switch - Google Patents

Description

; -5 9719 -2- The present invention relates to video signal switching, and in particular to that for applications such as stock exchanges.

Presently available video switches are generally in matrix 5 form having two sets of conductors, one of which forms the columns and the other the rows of a matrix. Individual switches are used for staking the desired connections.

Needless to say,, in cases where the switches are manually controlled, control of the video switch is extremely time-10 consuming. Even when the switches are electronically or electrically controlled problems arise in preventing interference between video signals, a large amount of space is required and complex control circuitry is required. Further, maintenance of the video switch is 15 difficult to achieve due to the complex construction and inter-dependence of the various connectors. When it is desired to route R, G and B video signals to various o different monitors, the control becomes extremely complex.

Finally? integration of known video switches into larger v 20 systems is often difficult as they require a dedicated controller. -3- The present invention is directed towards providing a video switch to overcome these problems.

According to the invention, there is provided a video switch compr i s i jag: ~ 5 a common input buffer circuit for reception and distribution of common input video signals,; a control circuit adapted to be operatively connected to a remote control unit; a switch circuit operatively connected to the control circuit comprising at least three multiplexer circuits, each having at least one dedicated input line for reception of dedicated input video signals, a plurality of common input lines for reception of common input video signals from the buffer circuit and one output line; a plurality of output amplifiers adapted to supply a video monitor; and 20 a link circuit operatively connected to the control circuit for linking the multiplexer output lines with the output amplifiers 10 15 according to desired configurations.

The invention will be more -clearly understood from the following description, of a preferred embodiment thereof given by way of example only with reference to the accompanying drawings irs which: - Fig. 1 is a perspective view from above showing the front of a video switch according to the invention; Fig. 2 is a perspective view from above showing the rear of the %rideo switch; Fig. 3 is a block diagram illustrating the operation of portion of the video switch; Figs. 4(a) to 4(f) are flow diagrams illustrating various output configurations of the video switch.

Referring to the drawings, and initially to Figs. 1 and 2, there is illustrated a video switch according to the invention, indicated generally by the reference numeral 1. The video switch 1 comprises a rack 2 having twenty slots 3 for reception of £©«sr buffer circuits 4 and sixteen switch circuits 5. Two power supply modules 6 are inserted to one side. The four buffer circuits 4 include a gain control potentiometer 7 for each of ninety common input video signals. Each switch circuit 5 comprises a -5- gain control potentiometer 8 for each of six input auxiliary signals and a gain control potentiometer 9 for each of six output signals. Each switch circuit S has three diagnostic LED8 s 16 and each power supply module 6 5 has two power supply level indicator LED°s 17. At the rear of the rack 2 there are six common input video signal connector sockets 10 of the MRAC type for reception of ninety common input video signals. Six MRAC sockets (not shown) are also provided for ninety common output video 10 signals. Six auxiliary input connector sockets 11 and six output connector sockets 12 are provided for each switch circuit 5. Power supply sockets 13 and circuit breaker switches 14 are also mounted at the rear of the power supply modules 6. The video switch is designed to operate 15 in a 50 MHjr bandwidth which is suitable for handling RGB colour video signals.

Referring to Figs. 3 and 4t» the video switch 1 is illustrated in more detail and parts similar to those described with reference to the previous drawings are 20 identified by the same reference numerals. Each of the buffer circuits 4 includes a multi-layer printed circuit board (PCB) with twenty-three buffer amplifiers with gain control over the range -6dB to 4-SdB. Each buffer circuit 4 also includes D.C. restoration circuits. To ensure that 25 gain control does not change with varying supply voltage, each of the buffer potentiometers 1 has voltage reference and op-amp multipliers to provide reference voltages. voltage reference and op-amp buffers are used for providing a bias voltage for clamp diodes and to D.C. offset the outputs of the amplifiers of the buffer * circuits 4. These amplifiers feed the ninety common input \. 5 video signals to each of the switch circuits 5.

Each switch circuit 5 is also connected to receive six auxiliary input video signals from the auxiliary input video signal sockets 11. Therefore, there is a total of ninety-six auxiliary input video signals and each of these 10 signals is dedicated to a particular switch circuit 5.

Each switch module 5, in turn, contains amplifier and gain control circuitry similar to that on the buffer circuit 4 for the auxiliary input video signals. Essentially, each switch circuit 5 comprises control circuitry, the above-15 mentioned amplifier and buffer circuitry and multiplexer circuitry. The multiplexer circuitry comprises sixteen-channel multiplexer integrated circuit (IC'») 30 (see Fig. 3) for reception of input video signals. The multiplexer IC's 30 are each connected to receive fifteen common input 20 video signals on lines 31 and one auxiliary input video signal on a line 32 to provide one output video signal on an output line 33. The output lines 33 are connected to a link circuit with plated-through holes so that the output video signals may be linked to a set of 6 output 25 amplifiers 35 depending on which conf igurat ion is required. -7- A aicroprocessor, not shown, is provided for controlling each switch circuit 5. The microprocessor communicates via level translators with the multiplex address logic and control latches. The address is a 4-bifc binary address 5 and the control logic consists of three independent logic inputs and a strobe input is used to control the latches. Address and enable bits are set up for a particular multiplexer 30 and this is then strobed, routing through the required channel. Any or all of the multiplexer 30 10 outputs can be disabled. Each switch circuit 5 is connected to an RS 485 serial port by the Microprocessor.

There are many possible configurations available for the output video signals from the multiplexer IC's 30. The simplest configuration is where the switch circuit 5 has 15. each of its output lines 33 connected to one output amplifier 35 (see Fig. 3). This configuration allows ninety-six monochrome input video signals to be switched to a single monochrome monitor 36. To route analogue RGB colour signals, the RGB input video signals are fed to 20 three consecutive multiplexer IC's 30. Referring to Fig. 4a the configuration is illustrated whereby two sets of three multiplexer IC's 30 are used to transmit RGB signals to three output amplifiers 35 connected to a single colour monitor 37. In this configuration there is a choice of 25 thirty-two RGB signals. To connect a switch module 5 to a colour monitor 37 and to a monochrome monitor 36, the conf igurat ion of Fig. 4(b) may be used. In this -8- configuration, two of the output amplifiers 35 are redundant and the monochrome nonitor 36 has access to forty-five common and three auxiliary monochrome input video signals and the colour saonitor 37 has access to 5 fifteen common and one auxiliary colour input video signal. It will be appreciated that there are many possible conf igurations for each of the switch modules 5 and that any number between one and six monitors may be supplied. The conf igurations illustrated are as follows:- 10 Fig. (4c) - sixteen channels for each of two colour monitors 37 Fig. (4d) - forty-eight channels for each of two monochrome monitors 36 Fig. (4e) - thirty-two channels for each of three 15 wonochrcsae Monitors 36 Fig. (4f) - sixteen channels for one colour monitor 37.

It will be appreciated that because these configurations may be easily controlled by a remote computer the video 20 switch of the invention is extremely versatile. -9- It will further be appreciated that because separate removable switch circuits are used, each of which receives common and dedicated input video signals, control problems in achieving a large number of output configurations are 5 overcome. A relatively simple control circuit on each switch circuit 5 may be used. Control is further simplified by the use of a number of multiplexer circuits which are arranged to simplify the transmission of synchronised R, G and B video signals. Essentially, 10 control of the video switch is achieved by the relatively simple control of each switch circuit 5 which can be arranged to drive between one and six separate monitors, either of the monochrome or colour types.

Reliability and ease of maintenance is achieved by the use 20 of integral power supplies and the interchaageability of the switch circuits 5. Potentiometers and other controls are readily accessible.

As the video switch way be controlled by a remote computer, several such video switches and other equipment 25 may be controlled centrally and thus the video switch may be integrated with ease.

Adjustment and repair work is relatively easy to carry out due to the modular construction of the video switch 1 and the accessability of potentiometers.

The invention is not limited to the embodiments hereinbefore described but may be varied in construction and detail.

Claims (7)

-11- CXAIHS

1. A video switch comprising:- a common input buffer circuit for recaption and distribution of common input video signals; a control circuit adapted to be operatively connected to a remote control unit; a switch circuit operatively connected to the control circuit comprising at least three 10 multiplexer circuits, each having at least one dedicated input line for reception of dedicated input video signals, a plurality of common' input lines for reception of common input video signals front the buffer circuit 15 and one output line; a plurality of output amplifiers adapted to supply a video monitor; and a link circuit operatively connected to the control circuit for linking the multiplexer 20 output lines with the output amplifiers according to desired configurations. -12-

2. A video switch as claimed in claim 1, in which the control circuit comprises means for synchronising at least one group of three multiplexer circuits to supply synchronised R, G and 3 video signals to 5 three output amplifiers.

3. A video switch as claimed in claim 2 in which the control circuit includes a microprocessor controlling a latch circuit for controlling operation of the multiplexer circuits. 10

4. A video switch as claimed in any preceding claim in which the control circuit includes a serial port for connection with a remote computer.

5. A video switch as claimed in any preceding claim in which there are a plurality of independent and 15 substantially similar switch circuits each removably mounted in a rack, and having dedicated buffer circuits for the input dedicated video signals.

6. A video switch as claimed in any preceding claim in 20 which, there is one output amplifier associated with each multiplexer circuit.

7. A video switch substantially as hereinbefore described with reference to and as illustrated in, -13- fche accompanying drawings. »1 ls Holies Street^ Dublin 2.