Abstract:
A modular mail processing method and control system that includes a plurality of induction transport modules and a stacker/transport module. The system maintains a real time statistics concerning the mail flowing through the system. The modularity of the system increases its flexibility in adapting to sorting either incoming or outgoing mail. In addition, a variety of readers and printers can be employed in the system to meet the needs of a particular customer.

Description:
This is a continuation of co-pending application Ser. No. 07/742,751 filed on Aug. 9, 1991, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a mail processing system; and in particular, to a modular mail processing method and control system. 
     Traditionally, mail processing systems are custom systems designed for a particular customer&#39;s needs. These systems are typically designed for high volume installations such as those that sort 30,000 to 40,000 pieces of mail per hour. With such large installations, custom designs to process either outgoing mail or internal mail are economically feasible. In these designs, the mail processing machinery and associated control system are fixed designs for the installation and are not easily modified for either future requirements or for the needs of other installations. Such custom designs are not economically practical for smaller installations that process in the range of 20,000 to 100,000 pieces of mail per day. There is therefore a need for a low cost, flexible processing system that can be inexpensively and quickly reconfigured to meet the needs of such low volume installations. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a low cost, flexible, modular mail processing method. 
     It is another object of the present invention to provide a low cost, flexible, modular mail processing control system. 
     It is still another object of the present invention to provide a modular mail processing method and control system capable of maintaining real time statistics regarding the mail processed. 
     It is still a further object of the present invention to provide a modular mail processing method and control system capable of processing mail at variable speeds. 
     It is still another object of the present invention to provide a modular mail processing method and control system capable of performing real time address correction. 
     To achieve the above and other objects, the present invention provides a method of processing pieces of mail in a system including a stacker module having a number of carriers and bins, including a feeder module, that are positioned to transport the pieces of mail from the feeder module to the stacker/transport module, the method comprising the steps of: (a) monitoring the position of each carrier; (b) selecting an empty carrier; (c) feeding a piece of mail from the feeder module to another induction transfer module at a desired time based on the position of the selected carrier; (d) tracking the position of the piece of mail through the induction transfer modules; (e) obtaining address information from the piece of mail; (f) selecting a bin for the piece of mail based on the address information; (g) transferring the piece of mail from a last induction transfer module to the selected carrier; and (h) diverting the piece of mail from the selected carrier to the selected bin. 
     The present invention also provides a modular mail processing control system for controlling the flow of mail through a series of induction transfer modules to a stacker/transport module that includes a number of carriers and bins, the system comprising: feeder means, located in one of the induction transfer modules, for injecting a piece of mail into another induction transfer module at a desired time based on a selected carrier being at a given position, and for identifying the piece of mail; encoder means, located in one of the induction transfer modules, for obtaining address information from the piece of mail and for identifying a bin for the piece of mail; tracking means, located in each of the induction transfer modules, for tracking the position of the piece of mail as it moves through the induction transfer modules, and in response to a position error stopping the series of induction transfer modules, storing the identification of at least the piece of mail involved in the position error and storing the position of the induction transfer modules of the stacker/transport module; inserter means, located in one of the induction transfer modules for inserting the piece of mail into the selected carrier when the selected carrier arrives at a desired location; and means for diverting the piece of mail from the carrier to the identified bin. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of an induction transfer portion of a mail processing system in accordance with the present invention; 
     FIG. 2 is a schematic diagram of a stacker/transport module in accordance with the present invention; 
     FIG. 3 is a schematic diagram of a modular mail processing control system embodying the present invention; 
     FIG. 4 is a schematic diagram of an embodiment of the modular processing control system software in accordance with the present invention; 
     FIG. 5 is a logic diagram of the bootstrap processing; 
     FIG. 6 is a flow diagram of the task scheduler; 
     FIG. 7 is a flow diagram of the manual feed terminal interface real time software module; 
     FIG. 8 illustrates the display at the system console during the manual feed process; 
     FIG. 9 is a simplified state diagram for the system state supervisor; 
     FIG. 10 is a logic flow diagram of the process performed to enable the system to perform a sort; 
     FIGS. 11A-11D illustrate the display at the system console during the FIG. 10 process; 
     FIG. 12 illustrates the display provided at the non real time CPU 275 when displaying the status of the system; 
     FIG. 13 is a logic flow diagram of the log on screen process shown in FIG. 10; 
     FIG. 14 is a logic flow diagram of the Enter Operators Processing shown in FIG. 10; 
     FIG. 15 is a logic flow diagram of the Choose Sort Type process shown in FIG. 10; 
     FIG. 16 is a logic flow diagram for the Choose Sort Plan processing shown in FIG. 10; 
     FIG. 17 illustrates a display as the non real time CPU 275 that occurs when an operator selects the reports option shown in FIG. 4; 
     FIG. 18 illustrates the display at the non real time CPU 275 when the operator selects the administration option; 
     FIG. 19 illustrates the display at the non real time CPU 275 when the operator selects the maintenance option; 
     FIG. 20 is a schematic diagram of the real time statistics maintained by the FIG. 3 controller; and 
     FIGS. 21A-21C provide an example of the type of information maintained by the non real time CPU 275. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is a schematic diagram of an induction transfer portion of a mail processing system in accordance with the present invention. In FIG. 1, reference numeral 20 identifies induction transport modules. As shown in FIG. 1, the induction transport modules are connected in series to form an induction transfer line 25 in FIG. 1, reference numeral 30 identifies an automatic feeder induction transfer module, reference numeral 35 identifies a manual feeder induction transport module, reference numeral 40 identifies an encoder induction transport module. The encoder induction transport module 40 feeds pieces of mail to an inserter induction transport module 45 which inserts the pieces of mail into a selected carrier 50 of a stacker/transport module 55. 
     FIG. 2 is a schematic diagram of a stacker/transport module in accordance with the present invention. The stacker/transport module 55 shown in FIG. 2 includes a number of bins 60. Referring to FIG. 1, an encoder 65 provides pulses to a control system (FIG. 3) identifying the location of carriers such as the carrier 50 within the stacker/transport module 55. The control system shown in FIG. 3 monitors the position of each carrier based on a number of pulses generated after the carrier is sent by a carrier number 1 sensor as shown in FIG. 2. Also shown in FIG. 2 is a chain stretch sensor 75. This sensor senses the amount of flex in a chain 80. A drive sprocket (not shown) can then be adjusted to take up the slack in the chain 80. 
     Referring to FIG. 2, when a carrier 85 reaches a selected bin 90, a diverter 95 is activated to move a rake 100 so as to engage the carrier 85; thus, deflecting the mail in the carrier 85 into the selected bin 90. 
     The control system shown in FIG. 3 controls the modular mail processing system shown in FIG. 1 so that a piece of mail injected into the induction transfer line by either the automatic feeder 30 or the manual feeder 35 reaches the selected carrier 50 when the selected carrier 50 is positioned to receive a piece a mail from the inserter induction transfer module 45. In a preferred embodiment of the present invention, the induction transfer line 25 operates at approximately 75 inches per second. The controller shown in FIG. 3, maintains the status of each carrier based on when a carrier is fed with a piece of mail and when a piece of mail is diverted out of a carrier. The FIG. 3 controller therefore selects an empty carrier based on this maintained status. The carrier empty sensor 110 and the carrier full sensors are used by the FIG. 3 controller to detect errors when the maintained status differs from the detected status of a carrier. The control system shown in FIG. 3 determines the distance of the empty carrier 105 from an arbitrary starting line 115 shown FIG. 2. The position of the starting line 115 is selected so that a carrier will arrive at the location adjacent the inserter module 45 in a position to receive a piece of mail from the inserter module 45 given a nominal rate of flow of a piece of mail through the induction transfer line 25. Thus, for example if the induction transfer line 25 is operating at a rate of 75 inches per second, and the length of the induction transfer line from, for example, the output of the auto feeder 30 to the output of the inserter module 45 is 25 feet, then the starting line 115 is positioned 25 feet from the point at which the selected carrier 50 arrives at a position with respect to the inserter module 45 to receive mail from the insert module 45. In such a case, when an empty carrier 105 reaches the starting line 115, then the control system shown in FIG. 3 would feed a piece of mail, via the auto feeder 30, to the induction transfer line 25. There is, of course, a different starting line for the manual feeder 35. Since the manual feeder 35 is closer to the desired position of the empty tray 105 adjacent the inserter module 45, the starting line for the manual feeder 35 would be closer to the inserter 45 than the starting line 115. Functionally, when an empty carrier reaches a starting line, the controller shown in FIG. 3 checks to see if there is a piece of mail to be fed by either the manual feeder 35 or the auto feeder 30. If there is a piece of mail to be fed into the induction transfer line 25, the FIG. 3 control system starts the appropriate servo motor at either the auto feeder 30 or the manual feeder 35. For example, if an empty carrier is at the starting line 115, and the auto feeder 30 has a piece of mail to insert into the induction transfer line 25, the FIG. 3 controller starts the servo motor 120 to feed a piece of mail into the induction transfer line 25. When a piece of mail is fed into the induction transfer line 25, the FIG. 3 controller stores an identification of the piece of mail together with the weight and thickness of the piece of mail. A series of sensors 125-152 are located amongst the induction transport modules 20. The sensors detect the presence of a piece of mail, and comprise, for example, through beam type sensors. Each piece of mail inserted into the induction transfer line 25 is individually identified by the FIG. 3 controller and tracked through the induction line 25. For example, when the auto feeder 30 is instructed by the FIG. 3 controller to insert a piece of mail, the leading edge of the piece of mail is detected by the sensor 125. If the piece of mail is traveling normally, then the FIG. 3 controller detects the trailing edge of the piece of mail passing the sensor 125. If the sensor 125 detects another piece of mail before the trailing edge of the current piece of mail leaves sensor 127, then a position error or jam situation exists. In such a circumstance, the FIG. 3 controller stores the identification of the current piece of mail as well as the other piece of mail and begins to shut down the induction transport modules 25 and the stacker/transport module 55. The FIG. 3 controller stops feeding mail to the transfer line 25. The FIG. 3 controller then stops all motors, and determines in which module the position error occurred. The motors at this point are slowing down towards a stop. The FIG. 3 controller informs the operator via the system console of the jam. The operator then removes the pieces of mail that need to be removed, and suppresses a system start button and responds to a system start button being pressed, the FIG. 3 controller turns all of the motors back on at a slow speed and waits until all of the mail is out of the induction transfer line 25 and into the appropriate carriers. At this point, the FIG. 3 controller turns all of the motors onto their normal speed and begins feeding mail normally. 
     The portion of the induction transfer line between the sensors 127 and 129 is an optional catch-up section 155. In this section, the FIG. 3 controller can adjust the position of the piece of mail based on the amount of movement that the selected carrier has undergone. In other words, the piece of mail in the catch-up section 155 has a desired position and an actual position with respect to the position of the carrier determined based on the output of encoder 65. The FIG. 3 controller can either accelerate or decelerate the piece of mail so that its position coincides with the desired position for the piece of mail. Referring to FIG. 1, when a piece of mail reaches the sensor 127, the FIG. 3 controller determines if a correction is necessary, and if so, how much. Once the trailing edge of the piece of mail is detected by the sensor 127, the FIG. 3 controller actuates a first catch-up servo motor 160. The movement of the piece of mail is thus accelerated or decelerated so that its position coincides with a desired position based on the position of the selected carrier within the stacker/transport module 55. When the leading edge of the piece of mail reaches the sensor 129, the position adjustment stops, and the piece of mail continues to move along the induction transfer line at its nominal rate (e.g., 75 inches per second). The induction transfer line 25 is driven at its nominal rate by 3 AC synchronous motors 165, 170 and 175 as shown in FIG. 1. While a piece of mail is between adjacent sensors such as 127 and 129, the FIG. 3 controller monitors for position errors (jams) as described with respect to sensors 125 and 127. Thus, adjacent sensor such as 125 and 127, and 127 and 129 function as sensor pairs that enable the FIG. 3 controller to track the position of the piece of mail through the induction transfer line 25 and to detect position errors in the induction transfer modules 20. 
     As shown in FIG. 1, an encoder 180 is coupled to the induction transfer line 25. The FIG. 3 controller uses the output of the encoder 180 to determine the position of the induction transfer line 25, or in other words, the position of the induction transfer modules 20. Thus, in the event of a position error detected, as noted above, the FIG. 3 controller determines the position of the induction transfer modules 20. Upon detecting a position error the FIG. 3 controller also determines and stores the position for the stacker/transport module based on the position indicated by the encoder 65. Thus, in the event of a position error the FIG. 3 controller stores the identification of the piece of mail involved in the position together with the position of the induction transport modules 20 and the stacker/transport modules 55. This enables the FIG. 3 controller to stop normal processing of the mail upon detecting a position error, and restart processing of the mail with the induction transport modules 20 and stacker/transport module 55 at their respective positions that existed at the time that the position error was detected. 
     As shown in FIG. 1, mail pieces can also be injected into the injunction transfer line 25 by a manual feeder 35. The manual feeder 35 includes a terminal 185, a cleated belt feed section 190 and a catch-up section 195. The catch-up section 195 includes a servo motor 200 together and with sensor 205 and 135 function in the same manner as the catch-up section 155. The operation of the manual feeder terminal 185 is described in detail below. Functionally, when an operator places a piece of mail in the cleated belt section 190, the FIG. 3 controller determines that the mail is present, its weight and thickness. This information together with an identification of the piece of mail is stored. When the FIG. 3 controller identifies an empty carrier 105 at the starting line for the manual feeder, as noted above, the FIG. 3 controller starts a servo motor 210 that causes the piece of mail to be pushed into the catch-up section 195. 
     As shown in FIG. 1, the encoder induction transport module includes a number of optional elements. Basically, the encoder induction transport module functions to read address information from the piece of mail and, together with the FIG. 3 controller to identify a bin 90 in the stacker/transport module 55 for the piece of mail. The address information can be detected from the piece of mail by either an optical character reader (OCR) 215 or a bar code reader (BCR) 220. There is, of course, no reason why both of these elements cannot be used in a system. This obviously would increase the cost, but enhance the flexibility of its system. The encoder induction transport module 40 can also include labeler 225, a bar code printer 230 and a verify bar code reading 235. The labeler 225 can be controlled by the FIG. 3 system to print the labels on outgoing mail. The labeler 225 can also be used for address correction. For example, if the OCR 215 reads address information and this address information is incorrect because the destination has been changed, a new label can be printed and applied to the piece of mail by the labeler 225. In addition, pieces of mail traveling through the system can have a bar code printed thereon for future sorting, either at another location or internally. The FIG. 3 control system includes a data base of addresses. This data base can be used to verify the address information read by either the bar code reader 220 or the optical character reader 215. If the destination address has been changed, then as mentioned, the labeler can apply a new label to the piece of mail. In addition, when the bar code reader 220 or the optical character reader 215 reads the address information from the piece of mail, the FIG. 3 controller identifies a bin 60 within the stacker/transport module 55 and stores this with the identification of the piece of mail. Thus, when the piece of mail reaches the selected carrier 50, the stacker/transport module moves the selected carrier 50 while the FIG. 3 system monitors the location of the carriers. When the selected carrier 50 arrives at the appropriate bin 60, the FIG. 3 control system activates the diverter 95 which causes a rake 100 to push the piece of mail out of the selected carrier and into the selected bin 90 as shown in FIG. 2. After the piece of mail leaves the encoder induction transport module, it enters the insert induction transport module 45. The inserter induction transport module functions to change the orientation of the piece of mail from vertical to horizontal for placement into the selected carrier 50. In addition, the inserter induction transport module 45 performs a catch-up function in catch-up section 240. The sensor pair 150 and 152 define the beginning and end of the catch-up section 240. It is not necessary to utilize each of the catch-up sections 155, 195 and 240. In fact, depending upon the type of mail flowing through the induction transport modules 20, it may not be necessary to have any of the catch-up sections. Basically, the catch-up sections 155, 195 and 240 function to adjust the position of the piece of mail which position may have been changed due to slippage of the belts within the induction transfer line 25. Such slippage could occur, by, for example, a thick piece of mail (e.g., 11/4 inches) encountering one or more of a series of dancer pulleys 245 shown throughout the induction transfer line 25. The structure of these pulleys is described in copending U.S. patent application entitled Induction Subsystem For Mail Sorting System by Stanley K. Wakamiya et al., filed Aug. 9, 1991, which is hereby incorporated by reference. 
     Because the FIG. 3 control system monitors the thickness of each piece of mail fed by the auto feeder 30 and manual feeder 35, it is possible to keep track of the total thickness of mail entered each of the bins 60. Thus, the FIG. 3 system maintains the height or total thickness of the mail in each bin 60. It is not necessary for the FIG. 3 control system to monitor the total thickness in this manner. Instead a sensor could be used to determine when a bin is full. When a bin 60 become 3/4 full, the FIG. 3 system flashes a warning light 250 that is associated with the 3/4 full bin 60. When the bin becomes full, the FIG. 3 system issues a warning by, for example, maintaining the warning light on all of the time; and also maintains any piece of mail destined for that bin in its carrier. In other words, any mail destined for a full bin stays in its selected carrier and circulates through the stacker/transport module 55 until its destination bin is emptied. To empty a bin, an operator pushes a bin button 255 to alert the FIG. 3 control system that the bin is being removed. The FIG. 3 control system also monitors a bin present sensor 260b to determine if there is a bin at a desired location. This is useful if, for example, an operator removes a bin without depressing the bin button 255. In addition, in some embodiments of the present invention when the FIG. 3 control system detects that a bin is full, the control system can activate a next bin actuator 265. This actuator moves the full bin out of its location and inserts an empty bin in its place. The stacker/transport module 55 moves the carriers 85 through the stacker/transport module 55 and past the inserter induction transport module 45 at the same rate that the induction transfer line 25 moves. This rate is variable and in one embodiment of the present invention corresponds to 75 inches per second. The rate is variable via operator control, and also in accordance with the state of the system. For example, if the system is recovering from an error then it moves at a much slower rate. 
     Since the FIG. 3 control system reads the address information from each piece of mail, identifies each piece of mail as it is fed into the induction transfer line 25, and selects an appropriate bin for the piece of mail, it uses this information to maintain on line statistics concerning the mail flowing the system. These statistics can include, for example, the number of pieces of mail sorted to each bin, the number of pieces of mail to each address (e.g., mail stop) or groups of addresses, the number of pieces of mail that were incorrectly read (e.g., the address information read by the bar code reader 225 or optical character reader 215 was not verifiable by the FIG. 3 control system). 
     The FIG. 3 system includes a set of sort plans. Each sort plan identifies which addresses should be placed in which bin 60 of the stacker/transport module. The operator can select, as discussed below, which sort plan is to be used on a particular sort run. Thus, when the encoder induction transport module obtains the address information from the piece of mail, the FIG. 3 control system searches the selected sort plan for the appropriate bin for the piece of mail placed in. 
     FIG. 3 is a schematic diagram of a modular mail processing control system embodying the present invention. The FIG. 3 control system includes two computers, a real time CPU 270 and a non real time CPU 275 that is connected to the real time CPU via an Ethernet link 280. The real time CPU controls the mail processing system via a VME bus 285. A serial port controller 290 interfaces a variety of devices with the real time CPU 270 over the VME bus 285. The serial controller 290 communicates with the variety of devices over a communication link identified in FIG. 3 as being an RS-232 connection. This is only one example and the communication can be of any other convenient type. As shown in FIG. 3, the serial controller controls communications between the real time CPU 270 and the bar code reader 220, the OCR 215, the labeler 225, the bar code printer 230, the verify bar code reader 235, a manual feeder scale 300 that is located in the manual feeder 35, and a manual feed terminal 185. The communication through the serial controller 290 is bi-directional for the labeler 225, bar code printer 230 and the manual feed terminal 185. The serial controller 290 interrupts the real time CPU 270 when one of the devices needs to communicate with the real time CPU 270. On being interrupted by the serial controller 290, the real time CPU 270 determines the source of the interrupt (e.g., manual feed terminal) reviews the data received from the device and generates either a message to internal real time CPU software and/or an output to the device. The internal messages are described in more detail below. An interrupt input circuit 305 collects interrupts from various sensors in the system (e.g., carrier empty sensor, the sensors 125-152), the control panel 310 and the servo motors. The interrupt input circuit 305 interrupts the real time CPU 270. The interrupt processing within the real time CPU 270 identifies the source of the interrupt, generates a message to internal real time software and/or an output to respond to the interrupt. All interrupts in the system are generated in a response to a physical event. For example, if an operator presses a system start button on the control panel 310, the interrupting input circuit 305 interrupts the real time CPU 270. Interrupt processing within the real time CPU 270 recognizes that the source of the interrupt is the system control panel and identifies that the system start button has been pressed. In response, the real time CPU generates a message for internal software such as the following. MSG --  SYS --  START that is sent to a system state supervisor. 
     The following table summarizes the interrupts generated by the interrupt input circuit. 
     
                       TABLE 1______________________________________Interrupt Designation              Description______________________________________ESTOP              Any of the various              emergency stop buttons              within the system is pushedInserterEntering   Input from sensor 150InserterLeaving    Input from sensor 152AF CatchUpEnter    Input from sensor 125AF CatchUpLeave    Input from sensor 127MF CatchUpEnter    Input from sensor 205CarrierEmpty       Input from carrier              empty sensor 110CarrierFull        Input from carrier              full sensor 111CNTL Panel.sub.-- Sys Stop              Control Panel 310              system stop buttonHandAwayMF         Output from safety              sensor 315 in the              manual feeder 35ChainStretch       Output of chain              stretch sensor 75CNTL Panel.sub.-- SysStart              System start button              at control panel 310              pushedMF MailPresent     Mail is present in the              manual feeder 35MLICR MailPresent  Output of sensor 135MF OverSizedLetter Output from the              pleated belt beat              section 190 of the              manual feeder 35Insert Jam Switch  Input from the insert-              er induction transport              module 45Carrier 1          Input from carrier 1              sensor 70AF MailPresent     Output from a sing              320 in the auto feeder              30MF TwistEnter      Output from sensor 205MF TwistLeave      Output from sensor 135MF MergeSuccess    Output of sensor 137MF InductionJam 1  Output of sensors in              the induction transfer              line 25MF InductionJam 2  Output of sensors in              the induction transfer              line 25MF InductionJam 3  Output of sensors in              the induction transfer              line 25MF InductionJam 4  Output of sensors in              the induction transfer              line 25MF InductionJam 5  Output of sensors in              the induction transfer              line 25MLICR Jam1MLICR Jam2Inserter Jam1Insert Jam2______________________________________ 
    
     TABLE 1 
     Each servo motor generates an interrupt when it acknowledges a command sent from the real time CPU 270. In addition, the real time CPU 270 is interrupted whenever a message is received over the Ethernet link 280. The scale 300 shown in FIG. 1 generates an interrupt when a piece of mail is placed on the cleat belt feet section 190. In addition, a counter/timer 325 generates interrupts for the real time CPU 270 whenever, for example, a counter finishes counting and/or a timer elapses. For example, the output of the encoder 65 in the stacker/transport module 55 is counted by a down counter. When the counter, for example, counts down to 0, an interrupt is generated to indicate that a particular carrier has reached a reference station. The counter is reloaded with the appropriate count so that an interrupt is generated when the next carrier arrives at the reference position. This technique permits variable spacing between the carriers. 
     As shown in FIG. 3, A to D converters 330 provide a digital output of the scale 300 to the real time CPU 270. In FIG. 3, reference numeral 335 designates a PAMUX I/O Bus controller. An embodiment of the present invention uses a XYCOM VME Bus PAMUX I/O type bus controller. This controller interfaces the sensors and actuators for the stacker/transport module 55, the lights and alarm indicators on the control panel 310 and the AC synchronous motors such as 165, 170 and 175 shown in FIG. 1. This controller also interfaces the real time CPU 270 with each of the servo motors so as to control the starting and stopping of the servo motors. Referring to FIG. 2, 3 bin modules in the stacker/transport module are illustrated. In each module, there is a diverter 95, warning light 250, bin present sensor 260, a bin button 255 and an optional next bin actuator 265 for each bin location. For the 27 bin stacker/transport module 55 shown in FIG. 2, these sensors and actuators require 135 input output lines. Thus necessitating a bus controller such as the PAMUX I/O bus controller 325. As shown in FIG. 3, the sensors and actuators as discussed above are isolated from the PAMUX I/O Bus Controller 335 by isolation modular boards 340. 
     FIG. 4 is a schematic diagram of an embodiment of the modular processing control system software in accordance with the present invention. The modular mail processing control software is structured, as shown in FIG. 4 into non real time software and real time software. The non real time software is associated with the system console associated with the non real time CPU 275. As schematically illustrated in FIG. 4, interrupt service routines (ISR) interface the real time software with the actual induction transport modules 20 and stacker/transport module 55. As mentioned above, each physical event in the induction transport modules 20 causes an interrupt. An interrupt service routine recognizes the source of the interrupt, issues a response to the source, and if needed generates a message to one of the modules of the real time software shown in FIG. 4. The message is passed amongst the real time software modules shown in FIG. 4 and the interrupt service routines and over the Ethernet 280s is in accordance with the known TCP/IP communication protocol. On powering up both the real time CPU275, the non real time CPU 275 enters a server listen mode, and waits for the real time 270 to issue a connect message. Upon receipt of the connect message, the non real time CPU 275 issues an accept message to establish a communication link over the Ethernet 280. The non real time CPU 275 begins the system console software as described in more detail below. 
     After establishing the session with the non real time CPU 275, the real time CPU 270 initializes each of the supervisor tasks shown in FIG. 4. This is accomplished by, and is explained in more detail below, placing a message MSG --  INIT in a message queue for each of these supervisors. The system task schedule is then started. This processing is schematically illustrated in FIG. 5 which represents the bootstrap processing performed in the real time CPU 270. 
     FIG. 6 is a flow diagram of the task scheduler. The task scheduler is a non-preemptive multi-tasking kernel which passes messages between supervisors and tasks shown in layer 2 of FIG. 4 and accepts messages from interrupt service routines shown in layer 1 of FIG. 4. These messages are passed through a series of message queues; each queue having a priority. Within each priority, the message queue functions as a first in, first out queue. As shown in FIG. 6, the task scheduler handles all of the messages in the current priority before continuing to the next priority. 
     FIG. 7 is a flow diagram of the manual feed terminal interface real time software module. In step S1, it is determined whether or not the current sort is an automatic sort or one which requires the operator of the manual feeder 35 to enter a mail stop. If it is an automatic mail sort, processing proceeds to step S6. In this step, a message is sent to the manual feed supervisor which then sends a message to the carrier scheduler to feed the piece of mail. The carrier scheduler will then place a message in the message queue for the interrupt service routines to activate the cleated belt servomotor 210 to begin feeding the piece of mail into the induction transfer line 25 shown in FIG. 1. Referring to FIG. 7, if mail stops should be entered by the operator of the manual feeder 35, the system requests that the operator enter a mail stop as shown in the screen illustrated in FIG. 8. If a mail stop is entered, processing proceeds to step S6 as described above. If a mail stop has not been entered, the processing proceeds to step S3 shown in FIG. 7. Referring to FIG. 8, the operator is prompted to enter a name in step S3 of FIG. 7. The names that match are then displayed by step S4 shown in FIG. 7. The operator chooses one of the names by entering the number associated with the desired name. If a name is chosen in step S5 of FIG. 7, then processing continues to step S6 as discussed above. Otherwise, the operator is requested to enter a name again in step S3 of FIG. 7. 
     The following describes the structure and operation of the layer 2 supervisors and tasks shown in FIG. 4; that is, the Manual Feed Supervisor, the Auto Feed Supervisor, the Read/Print (i.e. encoder) Supervisor, the Inserter Supervisor, the Stacker/Transport Supervisor, the Error/Jam Recovery Supervisor, the Carrier Scheduler and the System State Supervisor. Referring the FIGS. 1 and 4, the Manual Feed Supervisor controls the operation of the manual feeder 35 as schematically represented by the boxed portion of the system shown in FIG. 1. The auto feed supervisor controls the operation of the auto feeder 30 and portion of the induction transport modules 20 as schematically illustrated by the box shown in FIG. 1. The read/print (encoder) supervisor controls the operation of the read/print (encoder) induction transport module 40 as schematically illustrated by the box shown in FIG. 1. The inserter supervisor controls the operation of the inserter module 45 as schematically illustrated by the box shown in FIG. 1. The stacker/transport supervisor controls the operation of the stacker/transport module 55 shown in FIGS. 1 and 2. 
     In the following, each of the supervisors and tasks is discussed with respect to it&#39;s Moore machine state table which are to be read and together with the message data dictionary and Appendix A. In addition, Appendix A identifies each message used within the software shown in FIG. 4. The message name is shown in capitals and the parameter, if any is shown in lower case underneath the message name. In the Description portion of Appendix A names having a prefix &#34;isr&#34; identify interrupt service routines for example, referring to the description associated with the message MSG --  ESTOP in Section 1.1 of Appendix A, the source of this message is the interrupt service routine &#34;isrESTOP.&#34; Thus, the source of the input message MSG --  ESTOP is the interrupt service routine &#34;isrESTOP&#34;. The message is triggered by any one of the emergency stop (E-Stop) buttons being pressed on any one of the induction transfer modules 20 or the stacker/transport module 55. Where the parameter associated with the message MSG --  ESTOP is a boolean parameter that is true if the button is pressed and false if the button is not pressed or reset. 
     FIG. 9 is a simplified state diagram for the system state supervisor. Appendix B is the Moore machine state table for the system state supervisor. This state table is organized in the same way as all of the remaining state tables. There are four columns in each state table. The first identifies the present state, the second identifies the message input to that state, the third column identifies the next state, and the fourth column identifies the message output by the present state. The manual feed supervisor comprises two state tables. Appendix C is the state table for the manual feeder terminal 185 and cleat belt feed section 190 of the manual feeder induction transport module 35. Appendix D is the state table for the catch space up section 195 of the manual feeder induction transport module 35. The auto feed supervisor comprises three state tables. The first shown in Appendix E shows the auto feeder singulator 320. The second presented in Appendix F controls the actual catch up or position adjustment of a piece of mail within the auto feeder catch up section 155. The last state diagram for the auto feed supervisor is presented in Appendix G which controls the calculation of the amount of adjustment to the piece of mail that is to be made by the catch up section 155. The state machine shown in Appendix G also controls the general operational state of the catch up section 155 including its rev up, ramp down and stopping on a position error or jam detection as shown in Appendix G. The amount of position adjustment to be made by the catch up section 155 is based upon the difference between the desired position of the carriers within the stacker/transport module 55 and the actual position as determined by encoder 65. The difference between these two positions identifies the amount of position adjustment to be made by the catch up section 155. 
     The read/print (Encoder) supervisor state diagram is presented in Appendix H. The state diagram presented in Appendix H controls only the OCRN 215 shown in FIG. 1. 
     The inserter supervisor state machine actually comprises two state machines. Appendix K presents the state machine for the catch up section 240. This state machine controls when the position adjustment to be affected by the inserter induction transport module 45 should begin and end. The state machine shown in Appendix I is similar to that discussed with respect to the auto feed catchup date machine presented in Appendix F. That is, the Inserter supervisor state machine presented Appendix J controls the general operational state of the inserter and calculates the amount of position adjustment to be made by the inserter in the same manner as described with respect to the auto feed catch up section 155. 
     The Stacker/Transport Supervisor state machine is presented in Appendix K, and the Error/Jam recovery supervisor is presented in Appendix L. 
     The carrier scheduler is not a state machine and therefore Appendix M presents the pseudocode for the carrier scheduler. Both the manual feed supervisor and the auto feed supervisor send messages to the carrier scheduler via the task scheduler and associated message queues. These messages identify which of the feeders, the automatic feeder induction transport module 30 or the manual feeder induction transport module 35 has sent the request to feed a piece of mail. 
     In an embodiment of the present invention, the non real time software is implemented using Microsoft® windows. As shown in FIG. 4, on power up after the non real time CPU 275 and the real time CPU 270 establish a connection as described above, the non real time CPU 275 such as shown above the dotted line portion of FIG. 4. Basically, the non real time software has log on functions, sorting functions and system functions. FIG. 10 is a logic flow diagram of the process performed to enable the system to perform a sort. FIGS. 11A-11D illustrate the screens displayed by the non real time CPU 275 during the process illustrated in FIG. 10. FIG. 12 illustrates the display provided at the non real time CPU 275 when displaying the status of the system. 
     FIG. 13 is a logic flow diagram of the log on screen process shown in FIG. 10. In FIG. 13, the first step is to display the log on screen such as shown in FIG. 11A. At this point, the system waits for the operator to enter a password and a user name. The system then checks to see if the password matches the appropriate password for the user name. If not, the log on screen is again displayed. If the password and user name match, the sort and system menus shown in FIG. 4 are enabled and processing continues as shown in FIG. 10. As is common with programs written with Windows, if the operator selects either the OK area or the Cancel area, processing continues to the next process shown in FIG. 10. 
     FIG. 14 is a logic flow diagram of the Enter Operators Processing shown in FIG. 10. The first step is to display the inter operators screen. At this point, the system waits for the operator to enter at least one name. As discussed with respect to FIG. 11A, the operator can select either the OK or Cancel area and leave the operation. If the operator enters a name, the name is stored and processing continues as shown in FIG. 10. 
     FIG. 15 is a logic flow diagram of the Choose Sort Type process shown in FIG. 10. Referring the FIG. 11C and to FIG. 15, the sort mode screen is displayed first. The system then waits for the operator to choose one of the selections. If the operator chooses cancel, the processing continues as shown in FIG. 10 otherwise the selection is stored and processing continues as shown in FIG. 10. 
     FIG. 16 is a logic flow diagram for the Choose Sort Plan processing shown in FIG. 10. Referring the FIG. 16 and FIG. 11D the Choose Sort Plan Screen is first displayed. Next, the sort plans associated with the sort mode are displayed and the system waits for the operator to select a sort plan. If no sort plan is selected, the system start button on the control panel shown in FIG. 3 is nonfunctional. When the operator selects a sort plan, the selected sort plan is then sent to the real time CPU 270, and processing continues as shown in FIG. 10. More particularly, the status such as shown in FIG. 12 is displayed as the non real time CPU 275. 
     Referring to FIG. 4, a user has the ability to select system functions such as reports, administration (i.e. display of user information) as well as maintenance functions. FIG. 17 illustrates a display as the non real time CPU 275 that occurs when an operator selects the reports option shown in FIG. 4. The operator uses this screen to select which of the information stored by the FIG. 3 control system is to be printed. For example, the operator could print a distribution report showing the number of pieces of mail distributed to each of the bins shown in FIG. 2. 
     FIG. 18 illustrates the display at the non real time CPU 275 when the operator selects the administration option. This display promises the user to enter his name and password or to change the password. The display in FIG. 18 could restrict modification of the information based upon the status of the operator. For example, only an administrator could change the password. FIG. 19 illustrates the display at the non real time CPU 275 when the operator selects the maintenance option. 
     FIG. 20 is a schematic diagram of the real time statistics maintained by the FIG. 3 controller. As illustrated in FIG. 20, the statistics are maintained in a linked list fashion. FIGS. 21A-21C provide an example of the type of information maintained by the non real time CPU 275. 
     The many features and advantages of the invention are apparent from the detailed specification and thus it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention. ##SPC1##