Control module for engergy management system

• US 4,425,628 A
• Filed: 05/26/1981
• Issued: 01/10/1984
• Est. Priority Date: 05/26/1981
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Eichelberger, Charles W., Nati, Salvatore F. Jr., Miller, Edward B., Bedard, James F., Cutler, Scott E.
• Primary Examiner(s): Heckler, Thomas M.
• Application Number:
  US06/267,328
• Time in Patent Office: 959 Days
• Field of Search: 364/900 MS File, 364/492, 364/493, 315/291, 315/294, 315/312, 315/DIG. 4
• US Class Current: 710/8
• CPC Class Codes: H05B 47/18 via data-bus transmission

Abstract

A control module for controlling at least one variable-power-consuming load responsive to data input from local and/or remote locations, utilizes a controller microcomputer having an output setting the gain of a variable gain amplifier. The variable gain amplifier operates on a substantially-constant output of an oscillator to provide, on a cycle-by-cycle or long-term basis, a periodic waveform of controlled amplitude to the at least one load. The amplitude of the waveform sets the energy consumption/output of the load. Another data bus facilitates connection of local control means to a control module interface providing local control information to the controller microcomputer, while a third data bus is dedicated to communication with a remote central controller, if used. The control module includes circuitry for allowing a unique local address to be set for a particular control module, to which unique address the control module responds when a plurality of such control modules are connected in parallel to a central controller. A fourth data bus connects local sensors, such a photocells, thermistors and the like, through analog-to-digital conversion circuitry to the controller microcomputer, to facilitate control of the local loads responsive to local ambient conditions. The maximum level of the load(s) connected to a control module may be programmably established such that this maximum level can not be exceeded by local and/or remote commands, until the maximum level is altered.

Claims

1. Apparatus for providing a variable-characteristic signal for controlling the condition of at least one associated load to a selected one of plural levels of operation, said apparatus comprising:

(a) at least one local control means for providing load control means data signals and including at least one switching element having open and closed contact positions;

(b) controller logic means including a central processor unit (CPU), ROM means for substantially permanently storing program data defining operational parameters of the apparatus and for providing said program data under control of said CPU, RAM means for substantially temporarily storing digital data under control of said CPU, and input/output (I/O) means having ports for communicating digital data to and from the controller logic means;

(c) interface means responsive to a command from said CPU for interfacing said local control means data signal in digital form to at least one of said I/O means ports;

said interfacing means including an input bus to which said at least one local control switching element is connected;

(d) said CPU periodically requesting said local control means data signals from said I/O means in accordance with instructions contained in said ROM means program data;

(e) said RAM means receiving and storing the local control means data from said interfacing means until such data is requested by said CPU;

(f) said CPU producing digital data at least in part dependent upon the content of said local control means data signals;

(g) said RAM means receiving and storing said digital data; and

(h) means responsive to said digital data signals stored in said RAM means for producing said variable-characteristic signal with the magnitude of the variable characteristic being established responsive to said digital data obtained from said RAM means and for providing said variable-characteristic signal for controlling the condition of at least one associated load to a selected one of a plurality of at least three levels of operation.

2. The apparatus of claim 1, wherein said variable-characteristic signal is a variable amplitude signal.

3. The apparatus of claim 1, wherein said interface means further comprises a source of switch operating potential;

and a first resistance elements connected between said switch operating potential source and said input bus to cause said input bus to have a voltage thereon of first and second magnitudes responsive to said local control means switching element being in said open and closed contact conditions, respectively;

said at least one I/O means port having at least one input line for receiving said local control means data from said interfacing means.

4. The apparatus of claim 3, wherein said at least one I/O means port has at least one output line for providing a signal when said local control means data is to be input to said controller logic means;

and further including logic gating means receiving the voltage across said at least one local control means switching element for providing said controller logic means input with a digital signal, responsive to receipt of the signal at said controller logic means output line, of magnitude responsive to said first and second switch bus voltage magnitudes.

5. The apparatus of claim 4, further comprising a resistive voltage divider coupled between said input bus and said logic gating means to reduce the magnitude of voltage to a level compatible with said logic means.

6. The apparatus of claim 3, further comprising a resistive voltage divider coupled between said bus and said at least one I/O means port.

7. The apparatus of claim 1, wherein said local control means comprises a plurality of single-pole, double-throw switching elements, each having first and second switching portions actuatable to a closed condition in mutual-exclusive manner;

said at least one of said I/O means ports has a pair of data inputs, each associated with one of the first and second switching portions;

all of said first switching portions being connected in parallel to a first line of said local control means data bus;

all of said second switching portions being connected in parallel to a second line of said local control means data bus; and

a resistance element connected between said source of switch operating potential and each of said first and second data bus lines.

8. The apparatus of claim 7, further comprising first and second logic gating means each responsive to the signals on an associated one of said first and second data bus lines and to enablement of said output line, for providing a signal to the associated one of said first and second data inputs, indicative of the open or closed condition of any of the paralleled switch portions connected to the associated data bus line.

9. The apparatus of claim 8, further comprising first and second resistive voltage dividers coupled between an associated one of said first and second bus lines and the associated one of said first and second logic gating means to reduce the magnitude of the bus signals to a level compatible with said logic gating means.

10. The apparatus of claim 1, wherein said apparatus is also responsive to command data from a remote controller;

said apparatus including data bus means for enabling said apparatus to receive command data from said remote controller at another one of said I/O means ports.

11. The apparatus of claim 10, further comprising means for buffering command data received from said remote controller into data signals having levels compatible with said another one of said I/O means ports.

12. The apparatus of claim 11, wherein said buffering means includes an emitter follower circuit having an input connected to said bus and an output connected to said another one of said I/O means ports.

13. The apparatus of claim 10, wherein said remote controller bus is a bidirectional bus also allowing said apparatus to communicate digital data to said remote controller.

14. The apparatus of claim 13, further comprising means for buffering data signals from said another one of said I/O means ports into data signals having levels compatible with said data bus and said remote controller.

15. The apparatus of claim 10, further comprising means for designating a unique local address for said apparatus.

16. The apparatus of claim 15, wherein yet another one of said I/O means ports provides at least one signal for interrogation of said address designating means, responsive to a command from said CPU;

a portion of said RAM means being predeterminately established for storing the unique address data provided from said address-designating means responsive to the interrogation thereof;

said CPU comparing the address data stored in said RAM means portion to address data received from said remote controller as part of the command data therefrom and enabling said apparatus to respond to said remote controller command data only if the address data comparison is favorable.

17. The apparatus of claim 16, wherein said controller logic means is adapted for also storing data designating at least one of a universal address and at least one logical address and for comparing address data received from said remote controller for response thereto if said address data favorably compares to said at least one of said universal and logical address.

18. The apparatus of claim 16, wherein said load condition is the energy consumption/output of said load and said address designating means also includes means for designating a percent of maximum load consumption/output to which said load is to be set responsive to a load-on closure of said local control means.

19. The apparatus of claim 15, further including means for multiplexing the outputs of at least said address-designating means and said local control interfacing means to the same I/O means port.

20. The apparatus of claim 10, wherein said apparatus is also responsive to at least one analog-output sensing element external to said apparatus;

said apparatus further comprising ADC means for converting sensing element analog-output information to digital data for presentation to still another one of said I/O means ports, responsive to a command from said CPU.

21. The apparatus of claim 20, wherein at least one sensing elements includes at least one of ambient-light and ambient-temperature sensors.

22. The apparatus of claim 20, wherein said ADC means includes:

an integrating element;

a source of operating potential;

a resistance element in series with said integrating element across said operating potential source;

means for preventing said integrating element from operating unless an enabling command is received via said I/O means from said CPU; and

at least one comparator subcircuit having a first input receiving the voltage across said integrating element, a second input receiving the output of an associated one of said sensing elements, and an output enabled when a voltage across said integrating element is equal to the sensing element analog-magnitude;

the output of each of said sensing elements being associated with one of said comparator subcircuits.

23. The apparatus of claim 22, wherein said integrating element is a capacitor.

24. The apparatus of claim 22, wherein said switching means is a transistor.

25. The apparatus of claim 22, wherein each of said comparator subcircuits includes:

an operational amplifier having an inverting input, a non-inverting input and an output;

an input resistance element connected between said integrating element and a first one of said operational amplifier inputs;

a feedback resistance element connected between said operational amplifier output and the junction between said input resistance element and the associated operational amplifier input;

first and second resistance elements connected in series between said operating potential source and the remaining one of said operational amplifier inputs;

third and fourth resistance elements connected in series between ground potential and the junction of said first and second resistance elements;

said sensor being connected between ground potential and the junction between said third and fourth resistance elements;

a switching device having an input coupled to said operational amplifier output and an output circuit having a current flow therethrough controlled by the magnitude of the signal at said switching device input; and

a load resistance element coupled between said operating potential source and the output circuit of said switching device;

said comparator subcircuit output being obtained at the junction between said switching device and said load resistance element.

26. The apparatus of claim 1, wherein said apparatus is also responsive to at least one analog-output sensing element external to said apparatus;

said apparatus further comprising ADC means for converting sensing element analog-output information to digital data for presentation to still another one of said I/O means ports, responsive to a command from said CPU.

27. The apparatus of claim 26, wherein said at least one sensing element includes at least one of ambient-light and ambient-temperature sensors.

28. The apparatus of claim 26, wherein said ADC means includes:

an integrating element;

a source of operating potential;

a resistance element in series with said integrating element across said operating potential source;

means for preventing said integrating element from operating unless an enabling command is received via said I/O means from said CPU; and

at least one comparator subcircuit haviing a first input receiving the voltage across said integrating element, a second input receiving the output of an associated one of said sensing elements, and an output enabled when a voltage across said integrating element is equal to the sensing element analog-magnitude output;

each of said sensing elements being associated with one of said comparator subcircuits.

29. The apparatus of claim 28, wherein said integrating element is a capacitor.

30. The apparatus of claim 28, wherein said switching means is a transistor.

31. The apparatus of claim 28, wherein each of said comparator subcircuits includes:

an operational amplifier having an inverting input, a non-inverting input and an output;

an input resistance element connected between said integrating element and a first one of said operational amplifier inputs;

a feedback resistance element between said operational amplifier output and the junction between said input resistance element and the associated operational amplifier input;

first and second resistance elements connected in series between said operating potential source and the remaining one of said operational amplifier inputs;

third and fourth resistance elements connected in series between ground potential and the junction of said first and second resistance elements;

said sensor being connected between ground potential and the junction between said third and fourth resistance elements;

a switching device having an input coupled to said operational amplifier output and an output circuit having a current flow therethrough controlled by the magnitude of the signal at said switching device input; and

a load resistance element coupled between said operating potential source and output circuit of said switching device;

said comparator subcircuit output being obtained at the junction between said switching device and said load resistance element.

32. The apparatus of claim 1, wherein the controlled load condition is the energy consumption/output of said load.

33. The apparatus of claim 1, wherein each of said at least one load is a fluorescent lamp and activating ballast combination, and wherein the controllable load condition is the light energy output of said lamp.

34. A mehod for controlling the condition of at least one load to a selected one of multiple conditions, responsive to adjusting the magnitude of a load input control signal by actuation of a local control switch having selectable first and second closed positions and a normally open position, comprising the steps of:

(a) changing the magnitude of the load input control signal in a first direction responsive to any one of the at least one local control switch being in the first closed position;

(b) changing the magnitude of the load input control signal in a second direction, opposite to said first direction, responsive to any one of the at least one local control switch being in the second closed position;

(c) maintaining the magnitude of the load input control signal at a previously set magnitude responsive to all of the at least one local control switch being in the open position;

(d) sensing the load consumption/output level; and

(e) adjusting the magnitude of the load input control signal to maintain said load level substantially constant when said at least one local control switch is in the normally-open position.

35. The method of claim 34, wherein a control module is utilized for performing the steps of generating said control input signal responsive to the state of at least one local control switch.

36. The method of claim 35, wherein the controlled load condition is the energy consumption/output level of said load.

37. The method of claim 36, wherein the load energy consumption/output level of the load is increased responsive to an increase in said load input control signal.

38. The method of claim 37, further comprising the steps of:

specifying a maximum allowable load consumption/output level; and

limiting the magnitude of said load input control signal to never be greater than that load input control signal magnitude corresponding to the maximum allowable load output level.

39. The method of claims 37 or 38, further comprising the steps of:

specifying a minimum allowable load output level; and

limiting the magnitude of said load input control signal to never be less than that load input control signal magnitude corresponding to the minimum allowable load output level.

40. The method of claim 36, wherein the load energy consumption/output level of the load is decreased responsive to an increase in said load input control signal.

41. The method of claim 40, further comprising the steps of:

specifying a maximum allowable load consumption/output level; and

limiting the magnitude of said load input control signal to never be less than that load input control signal magnitude corresponding to the maximum allowable load output level.

42. The method of claims 40 or 41, further comprising the steps of:

specifying a minimum allowable load output level; and

limiting the magnitude of said load input control signal to never be greater than that load input control signal magnitude corresponding to the minimum allowable load output level.

43. The method of claim 36, further comprising the steps of:

positioning the at least one local control switch in the vicinity of the at least one load to be controlled; and

also controlling the increase and decrease of load output level from a central location, remote from said at least one load and at least one local control switch.

44. The method of claim 43, further comprising the step of inhibiting central-location-originated control if the at least one load is not previously energized.

45. The method of claim 43, further comprising the steps of:

receiving control information from the central location to set a maximum load output level; and

controlling the load output level to not exceed the maximum level set from the central location.

46. The method of claim 45, further comprising the step of allowing operation of the at least one load control switches to override the maximum level set from the central location.

47. The method of claim 43, further including the steps of:

providing the control module with a unique address;

transmitting the unique address from the central location whenever the control module is to respond to information originating at the central location; and

inhibiting the control module from responding to central-location-originated information unless the information is transmitted with the unique address previously assigned to the control module.

48. The method of claim 47, further comprising the steps of:

also providing the control module with at least one of a logical address and a universal address;

transmitting control information and logical or universal address data from the central location; and

enabling the control module to respond to data transmitted from the central location only if such data includes a logical address assigned to the control module or the universal address.

49. The method of claim 43, further comprising the steps of:

requesting information from the control module via a command from the central location; and

causing said control module to transmit the requested data to said central location.

50. The method of claim 36, further comprising the step of waiting, after each local control switch actuation for completion of that commanded change before accepting new load control information.

51. The method of claim 35, further comprising the step of gradually changing said load input control signal magnitude during, and in the direction of, the closure of any one of said at least one load control switch, to cause said load output level to gradually change in a corresponding manner.

52. The method of claim 35, including the step of resetting the control module to preselected initial conditions upon each application of operating power thereto.

53. The method of claim 34, wherein step (a) also includes the step of immediately changing the magnitude of the load input control signal to a preset level if the load was previously off and as soon thereafter as any one of the at least one local control switch is placed in the first closed position.

54. The method of claim 53, wherein step (a) further includes the step of increasing the magnitude of the load input control signal above said preset level, responsive to the continued presence at the first closed position of any one of the at least one local control switch.

55. A programmable system for controlling the energy output of plural electrically energized loads to ones of a plurality of discrete levels wherein a programmable central controller is coupled to distributed plural programmable control modules whose output means are respectively coupled to at least one subset of the loads, the combination comprising:

(a) the subset of electrically energized loads for producing a discrete level of energy output representative of the value of a control signal;

(b) the central controller for providing to the programmable control modules command digital data comprising commanded address data identifying the programmable control modules to be controlled by the central controller, and remotely commanded level data from the central controller representative of a selected one of a plurality of at least three discrete levels of load energization, including a turn-off level;

(c) the programmable control modules comprising means for internally storing address data, address recognition means for comparing commanded address data from said central controller with internally stored address data and means responsive to correspondence thereof for decoding the remotely commanded level data;

(d) local control switching means for connection to at least one of said programmable control modules to permit control of load energization from locations displaced from the central controller, said local control means comprising manually actuable switching means for locally commanding load energization to a selected one of a plurality of at least three discrete levels of energization, including a turn-off level;

(e) said at least one of said programmable control modules comprising means responsive to actuation of said local control switching means for generating and for storing locally commanded level data representative of the selected one of the plurality of at least three discrete levels of the load energization; and

(f) said at least one programmable control module comprising means for producing at its output means a load control signal of variable characteristic having a value representative of the last commanded one of remotely commanded level data and of locally commanded level data and for modifying the value of the control signal responsive to subsequent changes of either the locally commanded or the remotely commanded level data.

56. The arrangement of claim 55 for controlling the light-intensity of lighting loads, wherein the programmable control means comprises initiation means activated upon initial power turn-on for initially producing at the output means a control signal of a turn-on value representative of a predetermined level of light excitation intermediate light turn-off and of the maximum available lighting level.

57. The arrangement of claim 56 wherein said initiation means comprises means for presetting the magnitude of the turn-on value within a predetermined range of levels.

58. The combination of claim 55 comprising condition sensing means for providing a condition signal representative of the actual level of load energization, and wherein said programmable control modules comprise comparison means responsive to variations between the commanded level data and the condition signal for modifying the value of the control signal at the output means to provide coincidence between the commanded and actual levels of load energy output.

59. The combination of claim 58 comprising means for disabling said comparison means during intervals when the value of said output signal is varied responsive to modifications of commanded level data.

60. The combination of claim 58 wherein said condition sensing means is detachably coupled to the programmable control modules and the programmable control modules comprise means automatically responsive to removal of said condition sensing means for disabling said comparison means.

61. The arrangement of claim 58 wherein said programmable control modules comprise means for disabling said comparison means of a module during intervals when the subset of loads coupled to such module is turned off.

62. The arrangement of claim 58, wherein the condition sensing means provides an analog signal and said programmable control modules comprise means for producing a digital condition signal of a value corresponding to the value of the analog signal.

63. The arrangement of claim 62 comprising means for comparing the digital condition signal with the last commanded level data, means responsive to the value of said condition signal being representative of a level other than the commanded level for gradually modifying the value of said control signal until the level of load energy output corresponds to the commanded level.

64. The control system of claim 58 wherein the central controller can provide command digital data comprising a sensor read function code representative of a request for the value of the load energy output as sensed by the condition sensing means, and the programmable control modules comprise means for transmission of a digital sensor signal of a value corresponding to the value sensed by the condition sensing means coupled to the addressed one of the programmable control modules.

65. The arrangement according to claims 58, 59, 60, 61, 62, 63 or 64 for controlling the energy output of lighting loads, wherein said condition sensing means comprises light sensing means to provide a condition signal representative of the level of ambient light intensity.

66. The control system of claim 55 wherein the central controller can provide command digital data comprising a function code representative of a command to be performed by programmable control modules identified by the address portion of the digital command data, and said programmable control modules comprise means providing for execution of such command by addressed ones of the programmable control modules.

67. The arrangement of claim 66 wherein the function code is representative of a command to provide load excitation of a level specified by the remotely commanded level data provided by the central controller.

68. The arrangement of claim 67 wherein said programmable control modules comprise means for storing maximum level data representative of a selected maximum level of load excitation attainable by the associated subset of loads, and means for comparing commanded levels of load energization therewith and means for preventing the value of the control signal from attaining values representative of load excitation levels greater than the selected maximum value.

69. The arrangement of claim 67 for controlling the light intensity of lighting loads wherein the function code is representative of a command to slowly modify the level of light intensity, and said programmable control modules comprise means responsive thereto for slowly modifying the level of light intensity to the newly commanded value at a rate selected to minimize perception of the variation of light intensity.

70. The arrangement of claim 69 wherein said programmable control modules comprise means for storing data representative of a selected minimum level of light intensity, and means for limiting the value of the control signal to assure that the energy output of controlled loads is not decreased below this minimum level during slow modification of levels.

71. The arrangement of claim 69 wherein said programmable control means comprise means for gradually modifying the value of the output signal to provide for a gradual variation between two adjacent levels of light intensity, and responsive to commands for slow changes in excess of one level to consecutively provide for such gradual variation between consecutive adjacent levels until the newly commanded level is attained.

72. The arrangement of claim 66 wherein the function code is representative of a command to set a maximum level of load excitation to a value specified by the remotely commanded level data provided by the central controller, and said programmable control modules comprise means responsive thereto for storing maximum level data representative of the specified maximum level of load excitation and means responsive to comparing the values of commanded levels of load excitation and of stored maximum level data for preventing the value of the control signal from attaining values representative of load excitation levels greater than that of the specified maximum level.

73. The system of claim 72 wherein said programmable control modules comprise means responsive to a commanded reduction of the maximum level to a turn off level for modifying the value of the output signal to a value representative of turn off of the associated subset of loads.

74. The system of claim 72 for controlling the light intensity of lighting loads wherein said programmable control modules comprise means responsive to a commanded reduction of the maximum level to a level below the currently commanded level of load energization for gradually modifying the value of the control signal to provide for reduction of the light intensity produced by the respective subset of lighting loads at a rate selected to minimize perception of the variation of light intensity.

75. The arrangement of claim 66 wherein the central controller can provide command digital data comprising an interrogation function code representative of the value of specified parameters to be transmitted by addressed ones of said programmable control modules and said programmable control modules comprise means providing for the addressed ones of said programmable control modules to transmit the value of the specified parameter in conjunction with a predetermined module function code identifying the specified type of parameter.

76. The arrangement of claim 75 wherein the interrogation function code is representative of a request for the value of the maximum level data stored in the addressed ones of the programmable control modules.

77. The arrangement of claim 75 wherein the interrogation function code is representative of a request for the value of the currently commanded level stored in the addressed ones of the programmable control module.

78. The system of claim 66 wherein said programmable control modules comprise means for storing a first predetermined address adapted to uniquely identify said programmable control modules to permit said central controller to address selected individual ones of said programmable control modules.

79. The system of claim 78 wherein said programmable control modules comprise adjustable means for setting said first predetermined address to desired values.

80. The system of claim 79 wherein said programmable control modules comprise means for storing a second predetermined address common to each of said modules to permit said central controller to simultaneously address all of said modules.

81. The arrangement of claim 78 wherein said programmable control modules comprise means for storing an addtitional address of value commanded by said central controller, to permit the central controller to store additional addresses of common value in designated groups of programmable control modules and to thus simultaneously command such designated groups of modules.

82. The arrangement of claim 66 wherein the function code is representative of a command to store an additional address in addressed ones of the programmable control modules of a value specified by remotely commanded data provided by the central controller.

83. The arrangement of claim 82 wherein each of said programmable control modules also comprises means for storing a predetermined common address to permit said central controller to simultaneously address all of said modules, and further comprising means for comparing the commanded address data provided by the central controller with each of said stored addresses, and responsive to correlation thereof, to execute the function commanded by the central controller.

84. The system of claim 66 wherein said programmable control modules comprise means for storing an address common to plural ones of said control modules, and wherein the function code is representative of a load shed command to simultaneously reduce the level of energy output of subsets of loads coupled to plural ones of the programmable control modules that are simultaneously addressed by the central controller.

85. The system of claim 84 wherein the load shed function code is representative of a command to reduce load excitation to a load shed level specified by the remotely commanded level data provided by the central controller and the programmable control modules comprise means responsive to such load shed level being lower than the currently commanded level for modifying the control signal to a value representative of the load shed level.

86. A programmable lighting control system for controlling the light energy output of gaseous discharge tubes to selected ones of a plurality of discrete levels, the combination comprising:

(a) ballast means having an input, and an output adapted to energize a subset of gaseous discharge tube means to a level of intensity representative of the value of a signal applied to the input of the ballast means;

(b) programmable control means comprising;

(b1) output means,

(b2) input means for entering a command signal representative of a selected one of a plurality of discrete levels of light excitation;

(b3) means for producing a digital command signal of a value representative of the selected level;

(b4) means for converting said digital command signal to a corresponding variable characteristics signal;

(b5) means for generating and supplying at the output means a carrier signal modulated with the variable characteristic signal;

(c) coupling means coupled between the programmable control means and the ballast means comprising isolation means for coupling the variable characteristic output signal and for isolating d-c voltages occurring at the ballast means from the programmable control means, and

(d) detecting means coupled between the isolating means and the ballast means for providing to the ballast a unipolar signal of magnitude representative of the selected level of light intensity.

87. In a programmable lighting system wherein a plurality of ballast control modules located at dispersed locations are coupled to ballast means connected to gaseous discharge tube means, and wherein the ballast control means provides a control signal to the ballast means of a value representative of the desired one of a plurality of light excitation levels, said ballast control means comprising:

(a) first input means adapted to be coupled to a central controller for receiving therefrom digital data comprising address data and controller level data representative of a selected one of a plurality of at least three levels of light excitation to be produced by gaseous discharge tube means coupled to the ballast control modules;

(b) means for storing at least one preselected address;

(c) address recognition means responsive to reception of said digital data to compare the address data from the central controller with said at least one preselected address;

(d) means responsive to correspondence of address data with said at least one preselected address for storing the controller level data;

(e) second input means adapted for connection to local control switching means providing for local selection of one of a plurality of at least three discrete excitation levels;

(f) digital data means responsive to the local control switching means for producing local level data of a value representative of the locally selected level of light excitation; and

(g) output means for generating and producing a control signal of value representative of the level of the most recently received one of said controller level data and of said local level data, and for updating the value of said control signal responsive to the next subsequent receipt of either of centrally commanded or of locally commanded level data.

88. The arrangement of claim 87 wherein the local control switching means comprises at least one on/off electrical switch adapted to controllably close an electrical circuit coupled to said second input means, and wherein said digital data means produces local level data of a value representative of the time duration the electrical switch is actuated.

89. The arrangement of claim 88 wherein said second input means comprises first terminal means adapted for connection to incrementing switching means for increasing the current level of excitation, said ballast control means being responsive to actuation of the incrementing switching means to increment the level value of the locally commanded level data.

90. The arrangement of claim 88 wherein said second input means comprises second terminal means adapted for connection to decrementing switching means for decrementing the level of excitation, said ballast control means being responsive to actuation of the decrementing switching means to decrement the level value of the locally commanded level data.

91. A programmable system for controlling light excitation of gaseous discharge tube means to selected ones of a plurality of discrete levels of light excitation, the combination comprising:

(a) ballast means comprising an input adapted to receive a control signal, means for exciting gaseous discharge tube means to light excitation values inversely related to the value of the control signal and limited to a predetermined maximum excitation value in the absence of a control signal, and means for terminating excitation of the tube means during the presence of a control signal of a predetermined maximum value;

(b) ballast control means comprising output means for serial transmission of the control signal to the input of the ballast means, input means to receive a level command signal representative of a commanded one of a plurality of at least three discrete levels of excitation including a turn off level representative of a command to extinguish excitation of the gaseous discharge tube means;

(c) said ballast control means comprising means for providing at said output means a continuous control signal having a variable characteristic of a predetermined value that is representative of the commanded one of the plurality of levels and is inversely related to the ratio of the commanded level of excitation to the maximum excitation value producible by the ballast means.

92. In a system for controlling the light intensity of gaseous discharge tube means to a selected one of a plurality of at least three levels of discrete excitation, the combination comprising:

(a) ballast means comprising an input and means for energizing the discharge tube means to a level of intensity representative of the value of a control signal applied to said input;

(b) digital control means responsive to an externally commanded level of intensity to produce a digital control signal of value representative of the externally commanded level of intensity;

(c) modulation means for generating continuous waves modulated responsive to the value of said control signal;

(d) isolation means coupled between said modulation means and the input of said ballast means for isolating electrical potentials occuring at said ballast means from said modulating means; and

(e) detection means coupled in circuit between said isolation means and the input of said ballast means to provide to said input means a unipolar control signal of a magnitude representative of the commanded one of a plurality of discrete levels of light intensity.