United States Patent [19]
`Woodmas
`
`[75]
`[73]
`
`Inventor:
`Assignee:
`
`[54] SIGNAL TRANSFER AND POWER
`DELIVERY SYSTEM FOR A TELEVISION
`CAMERA STATION
`Charles D. Woodmas, Lyndon, Kans.
`Concept W Systems, Inc., Emporia,
`Kans.
`Appl. No.: 866,664
`Filed:
`Apr. 8, 1992
`
`Int. Cl.5 ............................................. .. H04B 3/54
`US. Cl. .................................... .. 455/3.3; 455/ 5.1;
`340/310 A
`Field of Search .................. .. 358/86; 455/3.1, 3.3,
`455/5.l, 6.3; 340/310 R, 310 A, 310 GP
`References Cited
`U.S. PATENT DOCUMENTS
`
`[21]
`[22]
`[5 ll
`[52]
`
`[58]
`
`[56]
`
`4,899,217 2/1990 MacFadyen et a1. ............... .. 358/86
`5,032,820 7/1991 Tanikawa et a1. ............ .. 340/ 310 R
`5,033,112 7/1991 Bowling et al. ........ .. 340/310 CP X
`Primary Examiner-Reinhard J. Eisenzopf
`
`USOO5345592A
`Patent Number:
`Date of Patent:
`
`[11]
`[45]
`
`5,345,592
`Sep. 6, 1994
`
`Assistant Examiner—Chi Pham
`Attorney, Agent, or Firm—Hovey, Williams, Timmons &
`Collins
`ABSTRACT
`[57]
`A television production system provides both signaling
`and power over a single coaxial cable between a televi
`sion control station and a remote camera station. The
`control station includes a power delivery unit for cou
`pling with the coaxial cable for delivering DC. voltage
`and current along with signaling over the coaxial cable.
`The camera station includes a power receiving unit
`which receives power from the coaxial cable and deliv
`ers it to the television camera and other camera station
`equipment. The receiving unit also monitors the re
`ceived voltage and provides a power status signal repre
`sentative thereof over the cable to the power delivery
`unit. The delivery unit controls the delivered voltage in
`accordance with the status signal in order to maintain
`the received voltage at the camera station at a desired
`level in order to compensate for cable voltage drop.
`
`31 Claims, 5 Drawing Sheets
`
`10
`
`16
`
`control station power deliver
`unit
`y
`
`14
`
`34
`
`control
`station
`
`power
`unit
`
`reception
`
`76
`
`18
`
`________________ _ __
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`contol station nodule )1
`26
`
`c?mef‘il
`station
`signal unit
`12 / 78
`
`/
`camera
`station
`
`nodule
`
`:
`
`24
`
`\_ ________________ _ _ _l
`
`

`
`U.S. ‘Patent
`
`Sep. 6, 1994
`
`Sheet 1 of 5
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`5,345,592
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`U.S. Patent
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`Sep. 6, 1994
`
`Sheet 2 of 5
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`5,345,592
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`US. Patent
`
`Sep. 6, 1994
`
`Sheet 4 of 5
`
`5,345,592
`
`( BEGIN )
`
`402
`/
`rINITIALIZE VARIABLES, DISPLAY ALARM;
`ACTIVATE PUWER UUTPUT AT LUW LEVEL
`440
`
`O (I) \_
`
`PULL DISPLAY SETUP
`SWITCHES; AND
`DISPLAY SWITCHES
`SETUP RUUTINE
`
`DISPLAY:
`‘ALERT-CHECK
`
`416
`\
`DISPLAY=\
`‘SIGNAL UNIT
`NUT READY FUR
`CABLE PUWER‘
`
`442
`
`DISPLAY:
`'AUTU PUWER
`NUW'
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`2”"‘4
`‘ EXECUTE ALARM
`PUWER-UN RUUTINE:
`CLEAR INTERRUPT
`MASK,- ENABLE CURRENT
`SURGE MUNITURING;
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`
`446 A
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`EXECUTE ‘WAIT’
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`ERUM PUWER STATUS SIGNAL.
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`DISPLAY: ‘SIGNAL UNIT
`READY F UR CABLE PUWER'
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`420
`DISPLAY:
`
`430
`
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`PRESENT‘
`I
`DISPLAY: ‘CAMERA
`428 Z UNIT
`/
`PRESENT‘
`
`EXECUTE ALARM
`SUBRUUTINE
`
`I
`
`A
`
`

`
`US. Patent
`
`Sep. 6, 1994
`
`Sheet 5 of 5
`
`5,345,592
`
`T
`
`D/A VALUE
`AT MINIMUM’?
`
`D/A VALUE
`AT MAXIMUM’?
`
`INCREMENT
`D/ A VALUE
`
`SIGNAL STATUS
`
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`
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`
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`EXECUTE DISPLAY
`SWITCH SUBRDUTINEJ
`DISPLAY=
`‘CHECK AND DISPLAY
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`
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`AT MINIMUM,‘
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`SWITCH.
`
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`DISPLAY:
`'ElUTPUT PEIWER
`ABURTED.‘
`
`TIME THRUUGH
`
`‘ YES
`EXECUTE ALARM
`SUBRDUTINE
`
`

`
`1
`
`SIGNAL TRANSFER AND POWER DELIVERY
`SYSTEM FOR A TELEVISION CAMERA STATION
`
`5
`
`5,345,592
`2
`More particularly, the invention hereof provides both
`signalling and power over a single conductor pair.
`Broadly speaking, the present invention includes re
`spective control and remote station modules operable
`for transferring signals between a conductor pair. The
`control station module includes a power delivery unit
`for delivering power to the conductors; the remote
`station module includes a power reception unit for re
`ceiving power from the conductors and delivering the
`power to the remote stations. The remote station mod
`ule also includes means for sensing the status of the
`power at the remote station, for producing the power
`status signal representative of the power status and for
`transferring the status signal to the conductors. The
`power delivery unit includes means for receiving the
`status signal and for controlling the delivery of power
`accordingly to the conductors.
`More particularly, the power status signal is represen
`tative of the D.C. voltage delivered to the power sta
`tion. The power delivery unit controls the D.C. voltage
`delivered to the conductors in order to maintain the
`desired remote voltage despite variations in power con
`sumption by the camera station and losses in the cable.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a schematic representation of a television
`production facility in accordance with the present in
`vention;
`FIG. 2 is an electrical block diagram illustrating the
`power delivery unit of FIG. 1;
`FIG. 3 is an electrical block diagram illustrating the
`power reception unit of FIG. 1;
`FIG. 4A is a computer program ?ow chart illustrat
`ing the operation of the microcontroller of FIG. 2; and
`FIG. 4B is a continuation of the computer program
`?ow chart of FIG. 4A.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`FIG. 1 is a schematic representation of signal transfer
`and power delivery apparatus 10 illustrated as part of
`television production facility 12 which includes control
`station 14 and camera station 16. Control station 14
`includes conventional television production equipment
`well known to_those skilled in the art such as the pro
`duction switcher, video and audio transmitters, camera
`monitors, preview monitors, program monitors, direc
`tor’s intercom, control signal generators, and control
`signal receivers. Camera station 16 is also conventional
`in nature and includes D.C. powerable video camera 18,
`talent earpiece 20, camera operator intercom headset
`22, and talent microphone 24.
`Apparatus 10 broadly includes control station module
`26 and camera station module 28 interconnected by
`conventional 75-Ohm coaxial cable 30. Control station
`module 26 is also coupled with control station 14 for
`bi-directional signal transfer therewith, and camera
`station module 28 is coupled with components 18-24 of
`camera station module 16 also for bi-directional signal
`transfer therewith.
`Control station module 26 includes control station
`signal unit 32 and power delivery unit 34. Signal unit 32
`is preferably a conventional signal multiplexing unit
`such as a CAMPLEX console adaptor available from
`Concept W Systems, Inc. of Emporia, Kans. Signal unit
`32 is operable to receive a plurality of signals from
`control station 14 and to combine and multiplex those
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`The present invention relates to the ?eld of television
`production using remotely located cameras. More par
`ticularly, the invention concerns a system for providing
`both signaling and power over a single coaxial cable
`between a television control station and a remote cam
`era station and for controlling the voltage delivered to
`the camera station.
`2. Description of the Prior Art
`On-location production of television programs typi
`cally involves the use of a production control center
`housed in a trailer or van connected with a number of
`remote camera stations by way of control and power
`cables. Each camera station typically includes a camera,
`camera operator headset, talent earpiece, and talent
`microphone. The control cables must have the capabil
`ity of carrying a wide variety of signals including cam
`era video and program audio signals from the camera
`station to the control facility, and two-way intercom
`audio between the control facility and the camera oper
`ator and talent. The cables also carry various control
`signals from the control center to the camera station
`such as system master reference signals including color
`black and a composite video signal (black burst) used as
`a synchronizing signal (gen-lock), and an on-air tally
`signal which activates the tally light on the camera
`viewable by the talent as an on-air cue.
`In one prior art cabling technique, 7a plurality of coax
`ial cables are used for carrying signals and power is
`provided to the camera station by a portable power
`35
`generator or conventional drop cords connected to the
`nearest A.C. outlet. The number of individual cables
`required for this technique can range from two to a
`more common seven consisting of four audio twisted
`pairs and three coaxial cables plus a power cord. As
`those skilled in the art will appreciate, a seven-line bun
`dle for one camera station weights about ninety pounds
`for a reach of three hundred ?fty feet.
`Another cabling technique uses a multi-conductor
`cable containing several narrow diameter mini-coaxial
`45
`cables and several wire pairs for audio and power. A
`more recent development uses a triaxial cable in which
`video and audio signals are modulated and multiplexed
`along the center conductor and the intermediate con
`ductor with power provided over the center and outer
`conductors.
`As those skilled in the art appreciate, all of these prior
`art cabling techniques are expensive and the cabling is
`relatively heavy and stiff making it awkward to carry
`and route. An even more recent technique is called the
`CAMPLEX system and uses a single coaxial cable over
`which all of the signalling is modulated and multi
`plexed. Because only a single coaxial cable is used, the
`use of this system is inexpensive and the single cable is
`very easy to carry, route and splice. This system does
`require, however, a separate power supply such as a
`conventional drop cord or the use of camera’s internal
`battery.
`SUMMARY OF THE INVENTION
`The signal transfer and delivery system of the present
`invention solves the prior art problems discussed above
`and provides a distinct advance in the state of the art.
`
`30
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`50
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`65
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`

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`20
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`5,345,592
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`4
`signals onto coaxial cable portion 36 for transmission to
`the connection therebetween coupled with microcon
`camera station 16 by way of power delivery unit 34 and
`troller 54 as an input thereto. The values of resistors
`camera station module 28. Similarly, unit 32 is operable
`72,74 are selected so that one tenth of the output voltage
`to receive multiplexed signals over cable portion 36 and
`from detector/limiter 44 is provided to microcontroller
`to separate the signals for presentation to control station
`54 as a representative signal thereof.
`14. In operation, preferred signal unit 32 imposes 12
`Signal separator and power combiner 48 includes
`VDC on line 36 when energized and imposes 24 VDC
`inductors L1 and L2 and capacitors C1 and C2 inter
`when activated for signal transfer. In the context of the
`connected as shown. Series connected inductor L1 and
`present invention, these two voltages are used as signals
`capacitor C2 form a low pass ?lter with an insertion
`indicative of the presence and signal operation of unit
`/isolation loss of about 10 dB at about 290 Khz which is
`32 as explained further herein.
`the frequency of the power status signal received by
`FIG. 2 illustrates power delivery unit 34 which, in
`combiner 48 over cable 30 from camera station module
`general, delivers power in the form of D.C. voltage and
`28 as explained further hereinbelow. Capacitor C1 in
`current to cable 30 for transmission thereover to camera
`terconnects cable portion 36 and cable 30 for passing
`station module 28 which then separates the power from
`the various signals therebetween unaffected by the de
`the signals for delivery to the appropriate components
`livery of power to cable 30 by power delivery unit 34.
`of camera station 16. Power delivery unit 34 includes
`Capacitor C1 forms a high pass ?lter with a 3 dB point
`variable output D.C. power supply 38, transformer 40,
`at about 1.0 Mhz to isolate control station signal unit 32
`current monitor 42, solid state switch and current surge
`from the power supplied to cable 30 by power delivery
`detector/limiter 44, voltage divider 46, ‘signal separator
`unit 34.
`and power combiner 48, RF choke 50, tracking ?lter
`As mentioned above, signal unit 32 also provides two
`and square wave generator 52, microcontroller 54, digi
`D.C. voltage outputs at 12 and 24 volts respectively
`tal-to-analog converter (DAC) 56, alpha-numeric dis
`corresponding to power-up and signal activation.
`play 58, display setup switches 60 and 62, and audible
`Choke 50 interconnects cable portion 36 at combiner 48
`alarm 64.
`and microcontroller 54 which allows the passage of
`these two voltages for monitoring by microcontroller
`Power supply 38 (Vicor FlatPAC VI-LE4-CW) re
`54 while preventing passage of the RF signals passing
`ceives 120 VAC power from a conventional source
`thereof and delivers an output D.C. voltage to common
`between control station and camera station 16. As ex
`mode transformer 40 (RENCO RL-1329-5-l000) used
`plained further hereinbelow, microcontroller 54 moni
`to remove high frequency noise from the output volt
`tors these two voltages provided by unit 32 in order to
`age. The output voltage from power supply 38 varies
`test for the presence and activation thereof.
`between about 15 and 48 volts in accordance with the
`Tracking ?lter and square wave generator 52 is a
`analog signal received from DAC 56.
`combination of a conventional phase locked loop (PLL)
`The input and output terminals of one leg of trans
`(EXAR XR-22l l), voltage comparator and binary rip
`former 40 are coupled to the respective inputs of cur
`ple counter. Generator 52 receives the power status
`rent monitor 42 which includes two reference diodes 66
`signal as an input from combiner 48. In turn, generator
`and 68 (LM336) and operational ampli?er 70 (NE5532).
`52 provides two outputs, the ?rst is in the form of a
`Diodes 66,68 provide calibrated voltage offsets to the
`“signal valid” output which indicates the presence of
`inputs of ampli?er 70. Monitor 42 detects the current
`the status signal to microcontroller 54.
`?ow from power supply 38 by monitoring the voltage
`The second output is in the form of a reduced fre
`40
`drop across the monitored leg of transformer 40 and
`quency square wave representative of the frequency of
`thereby provides an output voltage to microcontroller
`the input signal. This frequency represents the voltage
`54 between 0 and 5 VDC corresponding to a power
`‘provided to camera station 16 by camera station module
`supply output current ?ow between 0 and 2 amps.
`28 and is used by microcontroller 54 to control the
`Detector/limiter 44 receives the power flow from
`output voltage delivered to cable 30 by power delivery
`45
`transformer 40 and provides two levels of current limit
`unit 34. The conventional PLL is con?gured to operate
`ing. One level limits current to a low level at 15 milliam
`as a tracking ?lter tuned to lock to the status signal
`peres using two transistors conventionally con?gured
`which typically presents a frequency range from 250 to
`as a constant current ampli?er between the input and
`300 Khz. The output from the tracking ?lter’s oscillator
`output. As explained further hereinbelow, this low level
`is provided as the input to a voltage comparator
`of output power is applied to cable 30 when power
`(LM393) which converts the input to an output square
`delivery unit 34 is initially energized. The second level
`wave.
`of current limiting is for high level or operating power
`Passage- through the tracking ?lter and comparator
`and conventionally includes a power ?eld effect transis
`also provides selected ampli?cation, removes spurious
`signals, and provides a logic level square wave signal to
`tor (FET) (MTP8P10) used as a power switch and a
`second transistor (MPSA93) which monitors the volt
`the binary ripple counter (CD4024). This ripple counter
`age drop across a resistor in series with the FET power
`serves as a frequency divider (divide by 64) providing a
`switch as a current limiter. Detector/limiter 44 receives
`lower frequency square wave as an input to microcon
`a control input from microcontroller 54 which controls
`troller 54 which still retains the frequency variations of
`the input signal. The tracking ?lter also provides the
`the on-off status of the power switch but which can be
`over-ridden by the second transistor. In this way, detec
`“signal valid” output which is the “lock detect” output
`therefrom.
`tor/limiter 44 presents a self-contained current limiter
`which prevents large current surges in the high power
`Microcontroller 54 (Motorola MC68705R3), in addi
`output as might be caused by a short in cable 30 as a
`tion to the connections mentioned above, is also con
`result of being cut or pinched.
`nected to audible piezo alarm 64, to switches 60,62, and
`The output from detector/limiter 44 is coupled with
`to display 58 (available from Industrial Electronic Engi
`voltage divider 46 and combiner 48. Voltage divider 46
`neers, Inc. LCM-2006) as illustrated in FIG. 2. The
`is composed of series-coupled resistors 72 and 74 with
`operation of components 58-64 is explained further
`
`55
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`15
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`5,345,592
`6
`5
`hereinbelow in connection with the ?owcharts of
`a power-on state after the power input voltage is ad
`justed down to its normal level of 15 VDC.
`FIGS. 4A,B.
`Voltage threshold detector 90 comprises a zener
`Cable 30 interconnects control station module 26
`diode having the cathode coupled with the input to
`with camera station module 28 for bi-directional signal
`regulator 82 and having the anode thereof coupled to
`transfer therebetween and for delivery of power from
`the power control terminal of regulator 82. Detector 90
`power delivery unit 34. Camera station module 28 sepa
`prevents regulator 82 from supplying an output voltage
`rates the power from the signals on cable 30 and deliv
`until the input voltage rises above a threshold level of
`ers the power to camera station 16 for operational use.
`Camera station module 28 includes power reception
`24 VDC.
`Voltage regulator 86 includes two transistors con?g
`unit 76 and camera station signal unit 78. The preferred
`camera station signal unit is the CAMPLEX camera
`ured as a constant current ampli?er between the power
`adaptor available from Concept W Systems, Inc. of
`input and a zener diode coupled to ground at the power
`Emporia, Kans. with the circuitry of power reception
`output. Regulator 86 provides a clean and stable operat
`ing power supply to oscillator 88 at the power-in termi
`unit 76 integrated therewith to form a single integrated
`nal thereof.
`unit.
`Voltage controlled oscillator 88 (EXAR XR-2206)
`FIG. 3 is an electrical block diagram illustrating
`power reception unit 76 which includes signal combiner
`generates the power status signal as a frequency modu
`and power separator 80, current limited voltage regula
`lated signal between 250 and 350 Khz in accordance
`with the voltage applied to the control-voltage-in termi
`tor 82, current monitor 84, voltage regulator 86, voltage
`controlled oscillator 88 and voltage threshold detector
`nal corresponding to a range of 15 to 50 VDC. The
`voltage applied to this terminal is the D.C. voltage
`90.
`provided by separator 80 which in turn is the power
`Separator 80 includes inductors L1 and L2 and ca
`voltage as received from power delivery unit 34. In this
`pacitors C1 and C2 interconnected as shown. Capacitor
`way, the frequency of the power status signal represents
`C1 presents a high pass ?lter with a 3 dB point at about
`the voltage as delivered by cable 30 to camera station
`1 Mhz and thereby prevents passage of the DC. power
`module 28. As those skilled in the art will appreciate,
`voltage to camera station signal unit 78 but allows bi
`directional passage of the high frequency signals be
`the delivered voltage can vary according to the power
`draw of camera station 16 and the length of cable 30.
`tween cable 30 and signal unit 78. In contrast, series
`coupled inductors L1,L2 prevent passage of the high
`The power status signal represents the actual delivered
`voltage which is used by power delivery unit 34 to
`frequency signals but allow passage of the D.C. power
`compensate.
`as an output to regulators 82 and 84 as shown in FIG. 3.
`The power status signal produced by oscillator 88 is
`Conventional regulator 82 receives the power input
`coupled to cable 30 by way of inductors L1 and capaci
`from separator 80 and provides a current limited output
`tor C2 which form a low pass ?lter with an insertion
`at about 12 VDC to camera station 16 and in particular
`/isolation loss of about 10 dB at the frequency of the
`to camera 18. Regulator 82 uses a power ?eld effect
`status signal. With this con?guration of power recep
`transistor controlled by current monitor 84 to limit
`current throughput. More particularly, regulator 82
`tion unit 76, the status of the delivered power, that is,
`the DC. voltage thereof is sensed and a representative
`includes a zener-diode referenced operational ampli?er
`power status signal in the form of a frequency modu
`(NE5534) which functions as a power output voltage
`lated signal is transferred to cable 30.
`error ampli?er controlling a power ?eld effect transis
`FIGS. 4A,B are computer program ?owcharts illus
`tor (MTP8P10) which functions as a series regulator.
`trating the program for operating microprocessor 54.
`Regulator 82 is controlled by two signals. The ?rst
`signal is a power control signal received from voltage
`On power-up, the program enters at step 402 which
`initializes the software variables, inputs and outputs,
`threshold detector 90 which enables operation of the
`display 58 and alarm 64. This step also activates power
`error ampli?er and causes regulated power to pass
`delivery unit 34 to deliver a low level voltage to cable
`through the transistor. The second signal is a current
`30 at 15 VDC limited to 15ma. To accomplish this,
`control signal that controls a second transistor to over
`microcontroller 54 presents the appropriate binary code
`ride the error ampli?er output and thus controls the
`to DAC 56 which, in turn, produces an analog output to
`current through the power transistor.
`power supply 38 for producing the output at 15 VDC.
`Current monitor 84 generates a control signal used to
`activate the current limiting function of regulator 82.
`This low level is delivered to cable 30 by way of trans
`former 40, detector/limiter 44 and combiner 48. Detec
`Monitor 84 includes zener diodes 92 and 94 (LM336)
`tor/limiter 44 limits the output current to l5ma. By
`the anodes of which are connected to the input termi
`nals of operational ampli?er 96 (NE5230). The anode of
`limiting the output current to 15 ma, a short circuit in
`cable 30 causes the voltage thereon to drop from the
`output zener diode 98 (5.6 volts) is connected to the
`nominal 15 VDC which is detected by voltage divider
`output of ampli?er 96 and the cathode of diode 98 is
`46. When the voltage drops below 10 VDC, as repre
`connected to regulator 82 as a current control input
`sented by the signal delivered to microcontroller 54, a
`thereto. The cathodes of diodes 92,96 are connected
`short circuit is indicated as discussed further hereinbe
`across inductor L2 of separator 80 to detect the current
`induced voltage drop thereacross. The gain and offset
`low.
`Step 404 then asks whether control station signal unit
`of ampli?er 96 is calibrated such that a voltage drop
`32 is producing an output at 12 VDC as received by
`across inductor L2 equivalent to 2.0 amperes causes
`microcontroller 54 by way of cable portion 36 and
`output diode 96 to conduct and thereby enable the cur
`choke 50. As explained above, when control station
`rent limiting function of regulator 82. Power control
`signal unit 32 is initially energized, that is, powered up,
`diode 97 interconnects the output of regulator 82 with
`it produces an output at 12 VDC. This output is used by
`current monitor 84 at the power control terminal
`the program to determine whether signal unit 32 is
`thereof and with the output of threshold detector 90.
`present and powered.
`Diode 97 holds monitor 84 and voltage regulator 82 in
`
`50
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`40
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`45
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`

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`20
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`5,345,592
`7
`8
`If the answer in step 404 is no, step 406 activates
`options of voltage bar graph on, off, current bar graph
`display 58 to display the message “alert-check signal
`on, off or the combination voltage and current bar
`unit.” Step 408 then asks whether this is the ?rst time
`graph. When the desired menu option is displayed,
`through this portion of the program, and if yes step 410
`activation of “enter” switch 62 selects the display bar
`initiates execution of a conventional'alarm subroutine
`graph option for display. The program then loops back
`for activating audible alarm 64. The display and audible
`to step 404.
`alarm serve as a prompt to check the status of signal unit
`If the answer in step 436 is yes, then it is known that
`32. If the answer in step 408 is no, this indicates that the
`both control station signal unit 32 and power reception
`alarm subroutine was previously initiated and step 410
`unit 76 are ready for full power operation. Step 442 then
`can be skipped. The program continues to loop through
`displays the message “auto power now.” Step 444 then
`steps 404-410 until the presence of signal unit 32 is
`executes the alarm power-on routine and clears the
`indicated by a yes answer in step 404.
`interrupt mask. Step 444 also enables the current surge
`Step 412 then asks whether signal unit 32 is producing
`monitoring by detector/limiter 44 by providing an input
`an output voltage at 24 VDC indicating activation
`to the power control terminal thereof from microcon
`thereof for signal transfer. If yes, step 414 initiates dis
`troller 54. This action also closes the power transistor
`play of the message “signal unit ready for cable power.”
`and detector/limiter 44 which delivers full power out
`If the answer in step 412 is no, step 416 activates display
`put to cable 30.
`-
`58 for the message “signal unit not ready for cable
`Initially full power output is imposed at the lower end
`power.”
`of the allowable range (between about 15 and 50 VDC)
`After low level power output is initiated, step 418
`and step 446 then increments the output voltage by
`then asks whether the current output is less than the
`incrementing the binary code delivered to DAC 56.
`maximum allowable as indicated by the voltage signal
`The program then executes a standard wait subroutine
`received by microcontroller 54 from voltage divider 46.
`then asks in step 448 whether the output voltage as
`By limiting the output current to 15 ma, a short circuit
`delivered to cable 30 is at 48 VDC. If no, the program
`in cable 30 causes a voltage drop which can be detected
`continues to loop through steps 446 and 448, increment
`safely before full operating power is imposed. As those
`ing the voltage each time until 48 VDC is achieved
`skilled in the art will appreciate, a short circuit may
`taking about one fourth second to bring the voltage up
`result if cable 30 is pinched or cut, but may also occur
`to this level. When this occurs, step 450 again executes
`if the equipment at the remote end of cable 30 is defec
`the wait routine to allow the voltage to stabilize at
`tive or improperly connected.
`power reception unit 76.
`If the answer in step 418 is no, indicating that a short
`During this time, the solid state switch of regulator 82
`circuit does exist, step 420 initiates display of the mes
`(FIG. 3) is open and no power output is provided until
`sage “check load on cable.” Step 422 then asks whether
`the voltage reaches 24 VDC. At this point voltage
`this is the ?rst time through this loop of the program. If
`threshold detector 90 activates regulator 82 which be
`yes, step 424 initiates the alarm subroutine. If the answer
`gins producing an output at 12 VDC. In turn, this out
`35
`in step 422 is no, or after step 424, the program loops
`put latches in current monitor 84 and regulator 82 by
`back to step 418 and continues through steps 418-424
`way of diode 97. In step 452, microcontroller 54 then
`until the problem is corrected.
`reads the power status signal as presented by generator
`If the test in step 418 is passed, step 426 then asks
`52 from the square wave output terminal thereof. In
`whether the power status signal is present as detected
`40
`other words, in this step the program determines the
`by tracking ?lter and square wave generator 52. The
`voltage as present at power reception unit 76.
`presence of the status signal is provided to microcon
`The program next moves to step 454 in FIG. 4B
`troller 54 from the “signal valid” terminal of generator
`which asks whether the voltage as received by power
`52. When low level power is imposed on cable 30 and
`reception unit 76 is within the allowable range. A range
`power reception unit 76 is present and operational,
`is provided as a so-called “dead band” to keep the pro
`oscillator 88 (FIG. 3) senses the low level voltage deliv
`gram from “hunting.” If the answer in step 454 is yes,
`ered to reception unit 76, produces the power status
`the program moves to step 456 which displays the mes
`signal representative of the low level voltage and re
`sage “output power nominal.”
`turns the signal by way of cable 30 back to delivery unit
`If the received voltage is greater than the allowable
`34. In this way both the presence and functionality of
`range, step 458 asks whether the binary value to DAC
`50
`power delivery unit 76 are checked before full power is
`56 is already at its allowable minimum. If no, step 460
`imposed on cable 30.
`decrements the binary value.
`If the power status signal is present, step 428 initiates
`If step 454 indicates that the received voltage is less
`display of the message “camera unit present.” If the
`than the range, step 462 asks whether the binary value
`answer in step 426 is no, step 430 initiates display of the
`presented to DAC 56 is already at its maximum. If no,
`message “camera unit not present.”
`step 464 increments this binary value to increase the
`voltage.
`After steps 428 and 430, step 432 asks whether the
`voltage signal from camera station signal unit 32 is still
`If the answer in step 458 is yes, or after steps 460, 456
`at the high level voltage of 24 VDC. If no, the message
`or 464, step 456 asks whether the power status signal is
`“system standby” is displayed indicating that power
`60
`still present as indicated by the “single valid” output on
`delivery unit 34 is ready to deliver power. If the answer
`generator 52 (FIG. 2). If yes, step 468 then asks whether
`in step 432 is yes, step 436 again asks whether the power
`control station signal unit 32 is still activated as indi
`status signal is present. If no, step 438 displays the mes
`cated by its voltage output signal at 24 VDC.
`sage “system power ready.” After steps 434 or 438, step
`If the answer in step 468 is yes, step 470 then reads the
`440 polls setup switches 60,62 and in response, executes
`current output as represented by the signal from current
`the “display menu setup” routine. More particularly,
`monitor 42 and asks whether this value is greater than
`successive activation of “select” switch 60 causes dis
`the allowable two amps. If the current ?ow is below
`play 58 to successively display the ?ve bar-graph menu
`this allowable limit, the answer in step 470 is no and step
`
`55
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`65
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`25
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`45
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