Abstract:
An attachment for remote control of a plurality of data stations remote from each other and from a central controller having simple and convenient arrangements to put all the burden of powering and most switching of the attachment in the central controller. 
     A minimum number of transmission lines are used, yet it allows two-way data transmissions as well as a request-to-receive signal from any single remote data station to any of the remaining data stations, at the desire of the operator of the central controller.

Description:
This is a continuation of co-pending application Ser. No. 588,754 filed on Mar. 13, 1984, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention pertains to the field of data equipment interconnection. In greater particularity, this invention pertains to an arrangement to control the routing of data signal to a selected plurality of signal monitors. 
     2. Description of the Prior Art 
     Prior art method of interconnecting units of data equipment required that a separate means of transmitting perceptible signals, characterized by a pair of twisted wires and a coax cable, be used for each direction of transmission. 
     An example of this method is disclosed by U.S. Pat. No. 4,115,849. 
     Other prior art methods of interconnecting units of data equipment allows perceptible signals to be sent and received over a single cable by way of frequency conversion that shifts, for example, the transmit signal to a frequency located in a different portion of the spectrum of frequencies, away from the frequency used for the receive signal. These methods are used in different realizations of local-area networks that support a large number of channels of data, voice, and video by assigning different frequencies to each channel. 
     The drawbacks of operation of these prior art disclosures have been such that use of prior art circuitry has been always complicated and expensive in terms of manufacturing cost and mass productivity, even in the simplest configurations. 
     SUMMARY OF THE INVENTION 
     A general object of this invention is to provide, in relatively simple configurations, improved means for interconnecting units of data equipment without the drawbacks disclosed by prior art means. 
     A further general object of this invention is to provide, in relatively simple configurations, improved means for one master unit of data equipment to route signals generated at the master unit to a plurality of slave units of data equipment. 
     Another more specific object of this invention is to provide improved means for one master unit of data equipment to receive signals generated from any of the slave units of data equipment and send these very same signals to a selected plurality of the remaining slave units. 
     Yet a further object of this invention is to provide an improved means for one master unit of data equipment to request remotely a selected plurality of slave units to receive signals from the master unit. 
     Other objects, features and advantages of this invention will become more fully apparent hereinafter from the following description and drawings, which illustrate preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram explanatory of the interconnection between the master switching unit and the plurality of slave switching devices; 
     FIG. 2 is a schematic diagram showing the preferred construction of the master switching unit; 
     FIG. 3 is a schematic diagram showing the preferred construction of one amplifying means of the master switching unit; and 
     FIG. 4 is a schematic diagram showing the construction of one preferred embodiment of a slave switching device. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, numeral 1 indicates a master switching unit MSU; 2-1 to 2-n indicate n perceptible-signal transmission means, characterized by coax cables; 3-1 to 3-n designate n slave switching devices SSD1 to SSDn. Each transmission means 2-1 to 2-n has one of its ends connected to the master switching unit MSU by connecting means characterized by commercial-standard mating connectors 2-2-1 to 2-n-1. Numeral 4-0 designates a master signal monitor MMSO and 5-0 designates a master signal source MSSO characterized by a computer in output mode, both being connected to connectors 4-0-0 and 5-0-0 of the master switching unit, respectively. 
     Numeral 4-1 designates a slave signal monitor SSM1 and 5-1 designates a slave signal source SSS1, both being connected to connectors 4-1-0 and 5-1-0 of the slave switching device 3-1, respectively. Corresponding to this last description, a general numeral 4-j will be adopted to designate a slave signal monitor SSMj, and 5-j will be adopted to designate a slave signal source SSSj, both being connected to connectors 4-j-0 and 5-j-0 of the slave switching device 3-j, respectively. The adopted index j will take on values of 1,2,3 . . . n for a plurality of n slave switching devices. 
     FIG. 2 shows the schematic diagram of a preferred embodiment of the master switching unit. Connectors 2-1-0, . . . to 2-n-0, correspond to the same of like numerals in FIG. 1. A1 to An are perceptible signal amplifying means realizable by any state of the art circuitry. A preferred embodiment is shown in FIG. 3 for an example of video signal to be amplified in terms of current and power. In this very simple circuit, it can be seen that, with proper choice of resistors R1, R2, and transistors TR1 and TR2, any low power signal varying between 0 and 5 Volts DC applied between points IN3 and common electrical ground will cause a signal of appreciably higher power varying between 0 and about 5 Volts DC, respectively, to appear between point OUT3 and said ground. 
     Referring back to FIG. 2, a plurality of switches S that are differentiated by sub-numerals/alphabetic letters S1, . . . Sn designate preferably n switches of the single-pole, three position, for routing signals through the switches. These switches S for convenience of description are designated as secondary control switches in that they perform a second control function in the system. FIG. 2 being viewed in the upright manner, these three positions for each switch S1 to Sn are defined hereinafter as 
     position C1 when the movable center contact C of a switch is shorted to the upper one; 
     position C2 when no the center contact is not shorted to either the upper or lower one; and 
     position C3 when the center contact is shorted to the lower one. 
     It can be seen now that, for any switch S1 to Sn, designated hereinafter in all generality as Sj, (J=1, 2, 3, . . . , n), 
     position C1 will allow perceptible signals to be input to live I1 from the corresponding connector 2-j-0; 
     position C3 will allow perceptible signals at line O2 to be output onto corresponding connector 2-j-0; and 
     position C2 will leave perceptible signals on corresponding connector 2-j-0 untouched. 
     Always in FIG. 2, amplifying means B1, B2, and B3 are essentially made the same as any of the A1 to An. Hence, perceptible signals at line O2 are essentially the same as those at line O1, except with higher power. 
     The above said switchings of S1 to Sn provide partially the perceptible signal routing scheme. The remaining signal routing scheme is done by the device marked P in FIG. 2 and for convenience of description is designated the primary control switch. This switch P is preferably a 4-pole, 4-position switch. The 4 positions of this switch are designated as P1, P2, P3 and P4, starting from the very leftmost position in FIG. 2 and going clockwise. Each of the four poles, or sections, of the primary control switch P has a movable contact designated Pa, Pb, Pc and Pd, respectively. As is conventional for a switch of this type, the movable contacts may be mechanically intercoupled to enable their simultaneous displacement to the same selected one of the positions P 1 , P 2 , P 3 , or P 4  for effecting the signal routing as hereinafter described. 
     Following the signals around switch P in FIG. 2, it can be seen that 
     a. position P1 will input perceptible signals from connector 5-0-0 and output the same signals to connector 4-0-0, thus allowing the master signal monitor to display the signals of the master signal source; 
     b. position P2 will input perceptible signals from connector 5-0-0 and output the same signals to connector 4-0-0 and at the same time to line O2, and from there to each selected one or more of the slave signal monitors connected to connectors 2-1-0 . . . to 2-n-0, by way of position C3 of switches Sj, (j=1, 2, 3, . . . , n); 
     c. position P3 will input perceptible signals from line I1, therefore from any single selected slave signal source connected to one of the connectors 2-1-0 . . . to 2-n-0, by way of position C1 of this particular switch Sj corresponding to this connector, and output said signals to connector 4-0-0, therefore to the master signal monitor; 
     d. position P4 will input perceptible signals from line I1 and output the same signals to line 02 and to connector 4-0-0, therefore will input from any single slave signal source by way of position C1 of one of the switches Sj, and output to the master signal monitor and at the same time to selected or all other remaining slave signal monitors, again, by way of position C3 of the corresponding switches Sj of said selected or all other slave signal monitors. 
     Marking +5 VDC in FIG. 2 refers to the powering means of the master switching unit, having an adequate voltage with respect to ground, usually about +5 Volts DC, and having adequate power and regulation. 
     FIG. 4 shows one of the identical slave switching devices, having means for connecting and routing perceptible signals, implemented in the configuration where the slave signal monitors have their corresponding signal sources characterized by a computer in output mode. 
     Using the general index notation as above, numerals 2-j-1, 4-j-0 and 5-j-0 designate connectors of like numerals in FIG. 2 and FIG. 1. 
     Tj, (j=1, 2, 3, . . . n), designates a switching means of the single pole type having a movable center contact D and two positions defined as 
     a. position D1 when the center contact is shorted to the upper one; and 
     b. position D2 when the center contact is shorted to the lower one. 
     It can be seen that when a switch Tj is in position D1, perceptible signals input to connector 5-j-0 are routed directly as output to connector 4-j-0 and at the same time to connector 2-j-1. This means that if signal transmission means connected to connector 2-j-1 requires that signals be output at connector 2-j-1, everything will be all right and there is no perceptible change in the signals output to connector 4-j-0. However, it can be seen also that if signal transmission means connected to connector 2-j-1 requires that signals be input to the slave switching device at connector 2-j-1, when, in position D1, it receives signals from connector 5-j-0, it is obvious that connector 4-j-0 now receives two kinds of unrelated signals, and thus will cause the slave signal monitor connected thereto to loose synchronization in the display, and in general, to have its display torn apart in a drastic manner. In this invention, this loss of synchronization at a slave signal monitor is used systematically as a convenient way for the master switching unit operator to send the slave signal monitor operator a request to receive the signals, as well as the signals themselves routed to this slave switching device from the master switching unit. 
     It is intended in this invention when this loss of synchronization happens at a slave signal monitor, that the operator of the slave switching device push switch Tj to position D2 in order to get rid of the signals coming from connector 5-j-0, and to receive synchronously the signals coming from connector 2-j-1. After this, the end of request will make this slave monitor go black; and its operator may display again signals from connector 5-j-0 by pushing switch Tj to position D1. 
     It is clear now that by appropriate signal routing at the master switching unit, its operator can conveniently send a request to any slave switching device operator to receive, and at the same time and on the same cable the signals that, in turn, the master switching unit receives from any single one of the slave signal sources. 
     Numerous changes may be made in the above described arrangements and different embodiments of the invention may be made without departing from the spirit thereof; therefore, it is to be understood that all matter contained in the description and in the drawings shall not be construed as to limit the scope of the invention, which is limited only by the appended claims.