AU6054290A

AU6054290A - Auto/manual select means

Info

Publication number: AU6054290A
Application number: AU60542/90A
Authority: AU
Inventors: Gaylon Decious; Gerald A. Duenkel; Gregory A. Pascucci; Darrell E. Standish
Original assignee: Johnson Service Co
Current assignee: Johnson Service Co
Priority date: 1989-07-13
Filing date: 1990-07-11
Publication date: 1991-02-06
Anticipated expiration: 2010-07-11
Also published as: AU633127B2; WO1991001020A1; JPH04506582A; CA2057026A1; EP0558471A1

Description

AUTO/MANUAL SELECT MEANS

BACKGROUND OF THE INVENTION

The present invention is generally directed to an auto/manual select means for rendering a control system in either an automatic mode or a manual mode. The present invention is more particularly directed to such a select means for use in a control system which includes a processor for controlling at least one external device wherein the select means is selectable for selecting automatic control of the external device by the processor or ma ual control of the external device by an operator while also providing the processor with information indicative of the automatic or manual control selection.

Facilitymanagement systems are control systems which generally provide control of the internal environment and security and fire alarm monitoring of, for example, an office building or plant facility. Internal room temperature, humidity, air flow, lighting, security, and fire alarm are among some of the conditions controlled and/or monitored by such systems. Such control is usually provided through the control of external devices by a system processor. Many different types of external devices such as heaters, fan motors, dampers, humidifiers, and the like, may be employed and controlled for establishing desired set point conditions. Processors used to control these devices generally provide output control signals in a digital format. Since many different types of external devices are generally employed in a practical system, and since different types of control signals may be required to control the different types of external devices, interface circuitry is generally required between the system processor and the external devices to transform the digital output control signals of the processor to a form which is appropriate to control the various different types of external devices. The facility management system disclosed herein employs interface circuitry for this'purpose referred to as output function modules. Each output function module is adapted to transform the digital control signals from the system processor to a form which is adapted to provide suitable control of the external devices. For example, in accordance with one embodiment of the present invention, an output function module transforms the digital control signals of the system processor to opened or closed relay contacts. In accordance with another preferred embodiment, an output function module converts the digital control signals of the system processor to binary outputs having desired voltage levels. In accordance with another preferred embodiment, an output function module converts the digital control signals of the system process to an analog output having the desired voltage level .

In addition to the foregoing, it may be necessary to remove an external device from the automatic control of the system processor and to enable the external device to be controlled manually by an operator. Such a condition may arise in the unlikely event of system malfunction, when an external device is to be tested,or when some other suitable condition arises which requires manual control of an external device by an operator.

In the prior art, facility management systems have provided a selection of either automatic control or manual control of an external device. However, in prior 3 art systems,there was no provision for the system processor to be informed as to whether an external device was under manual control or automatic control. Such information would be desirable to be conveyed to the system processor so that,if an external device is under manual control,the system processor will annunciate this condition and react to the condition as defined by the system software. In this manner, the system processor will not only be informed as to the condition of the external devices which it controls, but in addition, processing time will be saved because the system processor need no longer address the external device under manual control.

SUMMARY OF THE INVENTION

The invention provides an auto/manual select means for use in a system which includes processing means for automatically controlling at least one external device. The auto/manual select means includes manually selectable means for selecting either automatic control of the external device by the processing means or manual control of the external device by an operator. The auto/manual select means also includes status means coupled to the selectable means and to the processing means for providing the processing means with information denoting the selected condition of the selectable means.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a block diagram of a control system embodying the present invention.

Figures 2A and 2B are schematic circuit diagrams which, when taken together, comprise a schematic circuit diagram of a first function module embodying the present invention and which may be utilized in the system of Figure 1.

Figures 3A and 3B are schematic circuit diagrams which, when taken together, comprise a schematic circuit diagram of a second function module embodying the present invention and which may be utilized in the system of Figure 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to Figure 1, it illustrates a control system 10 which may utilize the present invention to advantage, and, more particularly, a facility management system embodying the present invention. The system 10 generally includes a main communication bus 12, which may be an Nl LAN ARCNET bus, a network control module 14, a digital control module 16, and another bus 18, which may be an N2 OPTOMUX bus interconnecting the network control module 14 to the digital control module 16. LAN ARCNET and OPTOMUX buses 12 and 18 respectively are of the type well known in the art.

As illustrated in Figure 1, the system there shown includes just one network control module and digital control module for exemplary purposes, and it should be understood that additional network control modules and digital control modules may be connected to the main communication bus 12 in a practical system. This type of control system is referred to as a "distributed system", wherein each network control module is on a par with all other network control modules and communicates with all other network control modules on the bus 12. 5

The main function of the network control module is to communicate with the other network control modules of the system on an equal basis and to control its associated digital control module under its own assigned software protocol. Such a protocol may include setting temperature control set points, heating schedules, lighting schedules, et cetera. The network control module, in accordance with its protocol, sends high level commands to the digital control module which then executes on those commands by performing closed-loop operations by issuing suitable control signals at its outputs responsive to sensed input conditions by its remote sensors.

The digital control signals issued by the digital control module are preferably in digital form. The digital control signals issued by the digital control module are converted by output function modules to a format which may be utilized for controlling various different types of external devices which may be utilized within the system. For example, one type of output function module may convert the digital output signals to binary signals. Another output function module may convert the digital control signals to opened or closed contacts of a relay, and still another output function module may convert the digital control signals to an analog voltage. The function modules which provide opened or closed relay contacts may be used to activate fan motor starting windings or to turn on heaters. An output function module which provides an analog control signal can be used to power a damper motor to set a damper at a desired position. Hence, the digital control module performs decision-making processes, gathers information from its remote sensors, digitizes the information,digitally processes the information, and executes control functions to satisfy the high-level commands of the network control module.

The digital control module 16 thus processes digital information for performing various different types of closed-loop control operation within the system. To that egd, a digital control module 16 may include ten output channels identified as OCH1 through OCH10. The outputs OCH1 through OCH10 provide the control signals which are transferred and converted by the output function modules to control the various different types of controJL elements of the system, such as relays or damper motors, to provide the desired control of the internal environment of, for example, an office building. As previously mentioned, output function modules including relays controlled by the outputs of the digital control module 16 may, for example, turn on or off fan motors to establish desired air flow or heaters to establish desired room temperatures. Damper motors controlled by analog control signals provided by the' output function modules in response to the digital control signals of the digital control module 16 may be utilized to set a damper to also control air flow such as return air flow within a heating system.

In order to provide closed-loop control, the digital control modules 16 may include ten input channels CHI through CH10. These input channels receive various different kinds of information from remote sensors within the system, which remote sensors provide analog input information of various types indicative of the conditions being sensed by the remote sensors. Since the information provided by the remote sensors is in the form of analog information, the input channel CHI through CH10 are arranged to read analog input information. The analog information readable by each of the input channels is preferably a differential voltage.

Because various types of remote sensors may be required, the analog information provided by the remote sensors may be of various different types of analog information. For example, a temperature sensor may take the form of a temperature dependant resistance so that the temperature sensor provides a resistance having a magnitude which is indicative of the temperature being sensed. Other types of remote sensors may provide analog information of the condition being sensed in the form a voltage magnitude or current magnitude carried through a two-wire current loop. As a result, the system 10 preferably includes a universal analog input (IAU)_ 24 associated with each input channel CHI through CH10. The universal analog inputs 24 interface the remote sensors with the digital control module inputs to convert the various different types of analog information provided by the remote sensors to a given type of analog information, such as a differential voltage which is readable by the input channels CHI through CH10 of the digital control module.

To that end, the control system 10 of Figure 1 is illustrated as including a remote sensor 20 which is coupled to the first input channel (CHI) of the digital control module by an input interface which includes a terminal block 22 and a universal analog input circuit (IAU) 24. Similarly, another remote sensor 26 is shown coupled to the tenth input channel (CH10) by an identical terminal block 22 and an identical universal analog input circuit 24.

The terminal blocks 22 are adapted for connecting the remote sensors to the control system. The universal analog input circuit 24 provides an 8 interface disposed between the terminal blocks and the input channels. When the differential voltages at the input channels (CHI through CHIO are read, these differential voltages are converted to another analog 5 voltage having a magnitude indicative of the condition being sensed which is then received by the inputs of a data acquisition system within the digital control module 16. The data acquisition system thereafter converts the analog voltage to digital data in a bit-parallel format

10 for storage in memory and subsequent digital processing by the digital control module 16.

Since the digital control module includes ten output channels, it may perform up to ten separate closed-loop control operations. One such closed-loop

15 control operation is illustrated in Figure 1 in connection with the tenth output channel (OCH10) . Output channel OCH10 is coupled to an output function module 30. The output function module 30 preferably embodies the present invention, and, for purposes of this description,

20 will be assumed to be the output function module depicted in Figures 2A and 2B which provides open and closed relay contacts. The output function module 30 is coupled to a heater through a terminal block 34. When the relay of the output function module 30 closes,the heater 32 is

25 turned on for heating an internal space such as a room of a building.

The temperature of the room may be sensed by the remote sensor 26 which provides analog information in the form of a resistance having a magnitude indicative

30 of the temperature being sensed. The resistance analog information provided by the remote sensor 26 is coupled to the tenth input channel (CHIO) by the terminal block 22 and the universal analog input circuit 24. The temperature information from the remote sensor 26 is 9 converted from a resistance magnitude to a differential voltage by an interface formed by the terminal block 22 and the universal analog input circuit 24. When the differential voltage read at the tenth input channel (CHIO) indicates that the room being heated by the heater 32 is at the desired temperature dictated by the high- level command of the network control module, the digital control module 16 through output channel OCH10 will open the relay of the output function module 30 to turn off the heater 32. When the room temperature falls below the desired temperature, that condition is sensed by the remote sensor 26, is converted to a differential voltage by the input interface including terminal block 22 and the universal analog input circuit 24 to a differential voltage, which then causes the digital control module to close the relay of the output function module 30 by its output channel OCH10. The foregoing closed-loop process continues until it is interrupted by either an operator, manually placing the output function module 30 into a manual mode, or by a command from the network control module 14 to the digital control module 16 through the bus 18. In accordance with the present invention, if the output function module is placed in the manual mode, it will provide the digital control module with information indicative of the manual mode selection.

Referring now to Figures 2A and 2B, these Figures, when taken together, comprise a schematic circuit diagram of the output function module 30 illustrated in Figure 1 which embodies the present invention. The output function module 30 generally includes a bus interface 40, a data register 42, an output or driver section 44, and an auto/manual select circuit comprising a first portion 46a and a second portion 46b. The output function module 30 further includes three output lines 50, 52, and 54 which are adapted to be coupled to the external device to be controlled by the output function module through a terminal block as illustrated in Figure 1. As described with respect to Figure 1, the output function module 30 is of the type which includes a relay 48 which provides the external device coupled to the output function module with opened or closed contact conditions for controlling the external device. More specifically, when the relay 48 is energized, output lines 50 and 54 are coupled together and when the relay 48 is de-energized, output lines 50 and 52 are coupled together.

In general, the bus interface 40 couples the function module 50 to the digital control module 16 as illustrated in Figure 1. The bus interface 40 is coupled to the data register 42 and permits data to be written into the data register 42 of the output function module 30. The bus interface 40 also permits the digital control module to read the condition of the auto/manual select circuit 46a, 46b at section 46b to enable the auto/manual select circuit to inform the digital control module as to whether the output function module 30 is in the automatic mode or the manual mode. The data register 42 is coupled to the output circuit 44 for conveying the control signals from the digital control module to the output circuit 44 to the end of either energizing or de- energizing the relay 48 in accordance with the control signals. Hence, the output function module transfers the control signals of the digital control module to the external device to be controlled and converts the digital control signals to a suitable control format for controlling the external device.

When the output function module is placed into the manual mode by the auto/manual select circuit 46a, 46b, the first portion 46a of the auto/manual select circuit disconnects the output circuit 44 from the output lines 50, 52, and 54 and is utilized to manually duplicate the output conditions of the output lines 50, 52, and 54 obtainable with the energization or de- energization of the relay 48. This function will be described in greater detail hereinafter.

The bus interface 40 is coupled to a plurality of lines from the digital control module which include a line 56 which is used to initiate the reading of the condition of the auto/manual select circuit and to enable the writing of information into the data register 42, a line 58 which is utilized by the digital control module to select the function module 30 for addressing purposes, a line 60 to provide clock pulses for clocking data into the data register, and lines 62 and 64 which are by bi- directional lines which are utilized for conveying data into the data register from the digital control module to the function module and for conveying the condition of the auto/manual select circuit from the function module to the digital control module. The bus interface 40 includes a HAND gate 66, a NAND gate 68, NOR gate 70, NOR gate 72, and transistors 74 and 76. NAND gate 66 includes a first input which is coupled to the line 56 through a resistor 78 and a second input which is coupled to the output of NAND gate 68. NAND gate 68 includes a first input which is coupled to a positive 15 volt power supply and a second input which is coupled to line 58 through resistor 80. NOR gate 70 includes a first input which is also coupled to the line 58 through a resistor 80 and a second input which is coupled to the output of NOR gate 72. NOR gate 72 includes a first input which is coupled to the line 60 through a resistor 82 and a second input which is coupled to system ground. Transistor 74 includes a collector which is coupled directly to the line 62 and an emitter which is coupled to system ground. Similarly, transistor 76 includes a collector which is coupled directly to line 64 and an emitter which is coupled to system ground.

The data register 42 includes a pair of Dtype flip-flops 84 and -86. The clock input of flip-flop 84 is coupled to the output of NOR gate 70, the D-input of flip-flop 84 is coupled to line 62 through a resistor 88, and the S-input of flip-flop 84 is coupled to system ground. The clock input of flip-flop 86 is also coupled to the output of NOR gate 70, the D-input of flip-flop 86 is coupled to line 64 through a resistor 90, and the 5-input of flip-flop 86 is coupled to system ground. The auto/manual select circuit, as previously mentioned, includes two portions, 46a and 46b. The auto/manual select circuit includes a two section, three position switch comprising a first section 92a and a second section 92b. The switch sections 92a and 92b are ganged together. Each switch section includes two poles, switch section 92a including poles 94 and 96 and switch section 92b including poles 98 and 100. When the switch is in its first position as illustrated, pole 94 is in contact with contact 102, pole 96 is in contact with contact 104, pole 98 is in contact with contact 106, and pole 100 is in contact with contact 108. When the switch is in its second position, pole 94 is in contact with contact 110, pole 96 is in contact with contact 104, and poles 98 and 100 are opened as illustrated by the dashed lines. When the switch is in its third position, pole 94 is in contact with contact 110, pole 96 is in contact with contact 112, pole 98 is in contact with contact 114, and pole 100 is in contact with contact 116. The auto/manual select circuit portion 46b includes gate means comprising NOR gates 120 and 122. NOR gates 120 and 122 are coupled to the second section 92b of the auto/manual select switch and provide the status information in digital form to the digital control module in response to intermediate status signals provided by the second switch section 92b. To that end, NOR gate 120 includes a first input which is coupled to the output of NAND gate 66 and a second input which is coupled to contact 106 of switch section 92b and to a positive 15 volt power supply through a resistor 124. NOR gate 120 also includes an output which is coupled to the base of transistor 74 through a resistor 126. Similarly, NOR gate 122 includes a first input which is coupled to the output of NAND gate 66, a second input which ,is coupled to contact 116 of switch section 92b and to a positive 15 volt power supply through a resistor 126, and an output which is coupled to the base of transistor 76 through a resistor 128. The reset inputs of flip-flops 84 and 86 are coupled to a power-up reset circuit 130 through a resistor 132. The power-up reset circuit 130 includes transistors 134 and 136 which are arranged in a manner well known in the art. The power-up circuit 130 assures that when power is first applied to the output function module 30, the state of the flip-flops 84 and 86 will be in a known and predetermined condition.

The output circuit 44 includes, in addition to relay 48, a transistor 140. The base of transistor 140 is coupled to the Q-output of flip-flop 84 through a resistor 142. The emitter of transistor 140 is coupled to system ground and the collector of transistor 140 is coupled to one side of the relay coil 144 of relay 48. The other side of relay coil 144 is coupled to a positive 15 volt power supply through a resistor 146. When transistor 140 conducts, it completes a circuit from the power supply through the relay coil 144 and to ground to cause the relay 48 to be energized. When transistor 140 is back biased, and is thus off, the circuit path is disconnected for de-energizing the relay 48.

In operation, when data is to be read into the data register 42, the read-write line 56 goes high and the select line 58 goes low. Since the first input of NAND gate is tied to a high level, NAND gate 68 will provide a high level at its output which is impressed upon the second input of NAND gate 66. Since both inputs of NAND gate 66 are high, it will provide at its output a low-leveϋ which is impressed upon the first input of NOR gate 120. When the auto/manual select switch is in the automatic position, pole 98 is in contact with contact l 4 so that a high level will be at the second input of NOR gate 120. This will cause the output of NOR gate 120 to be low for back biasing the transistor 74. With transistor 74 back biased,the line 62 is available for presenting data to the D-input of flip-flop 84. At the next clock pulse, the first input of NOR gate 72 will be at a high level and together with the low level at its second input, the output of NOR gate 72 will be low. Both inputs of NOR gate 70 will be low to cause its output to go high to present a positive going clock pulse at the clock input of the flip-flop 84 for clocking the data on line 62 to the Q-output of flip-flop 84. If the data is a high level, the Q-output will go high to cause transistor 140 to be forward biased, and turned on for completing the circuit path from the positive 15 volt power supply through relay coil 144 and to ground to energize the relay 48. This causes, as previously mentioned, output lines 50 and 54 to be coupled together. If the data at the D-input of flip-flop 84 was a low level, the Q-output of flip-flop 84 will be at a low level which back biases and turns off transistor 140.

This causes the relay to be de-energized and for output lines 50 and 52 to be coupled together.

When the condition of the auto/manual select means is read by the digital control module in the automatic mode, the second input of NOR gate 120 is coupled to a high voltage level as previously described. Also, when in the automatic mode, pole 100 is in contact with contact 116. This causes the second input of NOR gate 122 to be coupled to system ground and provides that input with a low voltage level. Since the output of NAND gate 66 is low, both inputs of NOR gate 12 will be low causing its output to be high. The high level at the output of NOR gate 122 forward biases transistor 76 causing the line 64 to go low. Hence, when the function module is in the automatic mode, line 62 will be at a high level and line 64 will be at a low level to enable the digital control module to be informed that the function module is in the automatic mode.

As previouslymentioned, the auto/manual select switch is a three-position switch. The third position of the switch is for the automatic mode as previously described. The first position of the switch corresponds to a manual mode selection referred to as the "hand" position. In the "hand" position, the auto/manual select switch not only selects a manual mode, but in addition, couples output lines 50 and 54 together as if the relay 48 were energized. When in the "hand" position, the second input of NOR gate 120 is coupled to system ground and the second input of NOR gate 122 is coupled to the positive 15 volt power supply. When the condition of the auto/manual select means is read by the digital control module, the output of NAND gate 66 will go low to cause NOR gate 120 to provide a high-level output at its output. This high-level forward biases transistor 74 causing the bi-directional line 62 to go low. Also, the low voltage level from the output of NAND gate 66 is impressed upon the first input of NOR gate 122 to cause NOR gate 122 to provide a low level at its output to back bias transistor 76 to cause the bi-directional line 64 to be high. Hence, when the auto/manual select switch is in the manual "hand" condition, line 62 will be low and line 64 will be high. This condition is read by the digital control module so that the function module provides information to the digital control module indicative of the manual "hand" condition. When the auto/manual select ..switch is in its second position, the first switch section 92a duplicates the output conditions of the relay 48 when the relay is de-energized and causes output line 50 to be coupled to output line 52. This condition of the auto/manual select switch may be referred to as the "off" condition. As previously mentioned, in this condition, the poles 98 and 100 of the second switch section 92b are not coupled to any of the contacts of that switch portion to cause both of the second inputs of NOR gates 120 and 122 to be coupled to a high voltage level. When read by the digital control module, the output of NAND gate 66 is low to cause both NAND gates 120 and 122 to provide a low voltage level at their outputs for back biasing both transistors 74 and 76. This results in both lines 62 and 64 being high. Hence, function module 30, in accordance with the present invention, is capable of informing the digital control module as to the condition of the auto/manual select switch for each of the three separate selectable positions of the switch. As a result, the auto/manual select means of the present invention includes means for selecting respective different operating conditions of the external device connected to the function module including automatic control of the external device, a manual on condition of the external device, or a manual off condition of the external device, and wherein the auto/manual selection switch second section includes means for providing respective different intermediate status signals for each of the operating conditions of the external device. The NOR gates 120 and 122 in response to the intermediate status signals provide the final status signals to the transistors 74 and 76 to enable the reading of those conditions by the digital control module. Referring now to figures 3A and 3B, these figures when taken together comprise a schematic circuit diagram of another output function module 150 embodying the present invention. Function module 150 is adapted to provide a binary output at its outputs 152 and 154 wherein either output may source a current or sink a current. The function control module 150 includes the bus interface 40, the data register 42, and output circuit 156, and auto/manual select circuit 158. The bus interface 40 and data register 42 are identical to the bus interface and data register described with respect to Figure 2A and therefore need not be described in detail herein. As a result, the bus interface 40 is shown being coupled to the digital control module by the same plurality of lines 56, 58, 60,62 and 64 as previously described with respect to Figure 2A. Also, the data register 42 is coupled to a power-up reset circuit 130 as described with respect to Figure 2B.

The output circuit 156 comprises a pair of identical output circuit portions 156a and 156b. Since both output circuit portions are identical only output circuit portion 156a will be described in detail herein. Output circuit portion 156a includes a NAND gate 160, an invertor 162, an invertor 164, an invertor 166, and output transistors 168 and 170. The first input of NAND gate 160 is coupled to the Q output of 84 of data register 42. The output of NAND gate 160 is coupled to the input of invertor 162. The output of invertor 162 is coupled to the input of invertor 164 through resistors 172 and 174. The input of invertor 164 is also coupled to system ground by a capacitor 176 and to a contact of 178 of switch 180 through a diode 182. The switch 180 is a two-position push button switch and is shown in its open position. When the_ switch 180 is closed, the pole 182 will be in contact with contact 178. The switch 180 is utilized when the function module 150 is rendered in the manual mode as will be described in greater detail hereinafter.

The output of invertor 164 is coupled to the base of transistor 168. The emitter of transistor 168 is coupled to a constant voltage current fold back power source circuit 190 which is coupled to a positive 15 volt power supply. A diode 186 isolates the base of transistor 168 from the power source 190. The input to invertor 166 is coupled to the common node of resistors 172 and 174 and to the contact 178 of switch 180 through a resistor 192 and a diode 194. A capacitor 194 is also provided between the input of invertor 166 and system ground. The output of invertor 166 is coupled to the base of transistor 170 through a resistor 196. As will be noted from the figure, the collectors of transistors 168 and 170 are coupled together and to the output line 152 through a fuse 198. A zener diode is coupled between the collectors of transistors 168 and 170 and the emitter of transistor 170, which is also coupled to system ground.

When the function module 50 is in the automatic mode, the second input of NAND gate 160 will be at a high voltage level. As a result, the output of NAND gate 160 will depend upon the high or low level condition of the Q output of flip-flop 84. If the Q output of flip-flop 84 is at a high level, the output of NAND gate 160 will be at a low level. The output of invertor 162 will be at a high level and the output of invertor 164 will be at a low level. The low level output at the output of invertor 164 causes transistor 168 to be forward biased. Since the output of invertor 162 is at a high level, the output of invertor 166 will be at a low level to back bias transistor 170. As a result, transistor 168 will conduct current from the voltage source 190 out line 152 to the terminal blocks.

When the Q output of flip-flop 84 is at a low level, the output of NAND gate 160 will be high to cause the output of invertor 162 to be low. The output of invertor 164 will therefore be high and as a result, the transistor 168 will be back biased. Because the output of invertor 162 is low, the output of invertor 166 will be high to forward bias transistor 170. Hence, transistor 168 will not conduct but transistor 170 will conduct. As a result, the output line 152 will be pulled down to a low voltage level.

The auto/manual select circuit 158 includes an auto/manual select switch 202, a NOR gate 204 and another NOR gate 206. The switch 202 is a single pole two position switch having a pole 208 and contacts 210 and 212. The contact 210 is coupled to a positive 15 volt power supply through a resistor 214 and to the second input of the NOR gate 204. The first input of NOR gate 204 is coupled to the output of NAND gate 66 of the bus interface 40. The output of NOR gate 204 is coupled to the base of transistor 74 through the resistor 126. The contact 212 is coupled to a positive 15 volt power source through a resistor 216 and to the second input of NOR gate 206. The first input of NOR gate 206 is also coupled to, the output of NAND gate 66 of bus interface

40. As can be noted from the Figures, the contact 210 is also coupled to the second inputs of NAND gate 160 and NAND gate 161 of the output circuit second portion 156b. The output of NOR gate 206 is coupled to the base of transistor 76 of the bus interface 40 through the resistor 128.

When the auto/manual select switch is positioned to select the automatic mode., the pole 208 is in contact with contact 212. This causes the second input of NOR gate 204 to be at a high level and the second input of NOR gate 206 to be at a low level. Because a low level is impressed upon the first inputs of NOR gates 204 and 206 when the condition of the auto/manual select circuit is conveyed to the digital control module, the output of NOR gate 204 will be at a low level .and the output of NOR gate 206 will be at a high level. These levels cause transistor 74 to be back biased and transistor 76 to be forward biased. As a result, the automatic mode is selected,the bi-directional line 62 will be at a high level and bi-directional line 64 will be at a low level indicative of the automatic mode selection. In the manual mode, the auto/manual select switch 202 is in the position illustrated. This causes the second input of NOR gate 204 to be at a low level and the second input of NOR gate 206 to be at a high level. As a result, the output of NOR gate 204 will be at a high level and the output of NOR gate 206 will be at a low level. These levels cause transistor 74 to conduct and transistor 76 to be turned off. As a result, the bi-directional line 62 will be at a low level and bi¬ directional 64 to be at a high level indicative of the manual mode selection.

When the auto/manual select circuit is conditioned to select the manual mode, the second inputs of NAND gates 160 and 161 will be at a low level so that regardless of the level of the Q outputs of flip-flops 84 and 86 of the data register 42, the binary voltage level at the outputs 152 and 154 will depend upon the condition of the switches 180 and 181. For example, if switch 181 is in the position illustrated, that is, its open position, then the binary output at output line 152 will be at a low level. This results because the second input of NAND gate 160 is at a low level causing its output to be at a high level. This in turn causes the output of invertor 162 to be at a low level and the output of invertor 164 to be at a high level. The output of invertor 166 will also be at a high level so that transistor 170 will conduct and transistor 168 will be turned off. This results in the output line 152 being pulled down to a low level.

When switch 180 is closed and pole 182 contacts contact 178, a high voltage level will be impressed upon the inputs to invertors 164 and 166 through resistors 174 and 192 respectively. This causes the outputs of invertors 164 and 166 to be at a low level to forward bias transistor 168 and back bias transistor 170. As a result, current will flow through transistor 168 and out line 152 to the terminal blocks.

As a result of the foregoing, the function module 150 of this embodiment provides the selection of either an automatic or manual mode condition of the function module. The function module 150 provides the digital control module with information indicative of the manual or automatic mode selection. When in the automaticmode, line 62 is high and line 64 is low. When in the manual mode, line 62 is low and line 64 is high. In addition, when in the manual mode, control of the external device ils removed from the digital control module by the NAND gates 160 and 161 to place the outputs under the control of the manual switches 180 and 181. While particular embodiments of the present invention have been shown and described, modifications may be made, and it is intended in the appended claims to cover all such modifications as may fall within the true spirit and scope of the invention.

Claims

What is claimed is:

1. An auto/manual select means for use in a system which includes processing means for automatically controlling at least one external device, said auto/manual select means comprising: manually selectable means (46a; 158) for selecting either automatic control of said external device by said processing means or manual control of said external device by an operator, and status means (46b; 204,206) coupled to said selectable means and to said processing means for providing said processingmeanswith informationdenoting the selected condition of said selectable means.

2. An auto/manual select means as defined in Claim

1 wherein said manually selectable means comprises switch means (92a; 202) .

3. An auto/manual select means as defined in Claim

2 wherein said status means comprises gate means (120,122; 204,206) coupled to said switch means for providing said status information in digital form.

4. An auto/manual select means as defined in Claim 1 wherein said manually selectable means comprises switch means (92a; 92b) including a first switch section (92a) for selecting said automatic or manual control and wherein said status mens comprises a second switch section (926) operable with said first switch section for providing intermediate status signals.

5. An auto/manual select means as defined in Claim

4 further comprising gate means (120, 122) coupled to said second switch section (92b) for providing said status information in response to said intermediate status signals.

6. An auto/manual select means as defined in Claim

5 wherein said switch means first section (92a) includes means (102, 104, 110, 112) for selecting respective different operating conditions of said external device including automatic control of said external devices, a manual on condition of said external device, or a manual off condition of said external device, and wherein said switch means second section includes means (106, 1_08, 114, 116) for providing respective different intermediate status signals for each of said operating conditions of said external device.

7. An auto/manual select means as defined in Claim 6 wherein said switch means (92a, 92b) comprises a two-sectionmechanical switch, said switch being a three-position switch.

8. An auto/manual select means as defined in Claim

6 wherein said switch means second section (92b) includes first and second subsections

(98, 100) and wherein said gate means includes a first gate (120) coupled to said first subsection and a second gate (122) coupled to said second subsection, each of said gates including an output, and wherein said gate outputs provide said status information for each of said operating conditions of said external device.