Abstract: An improved electronic postage meter which includes a microcomputer (17), redundant memories ("BAMs") (35a-b), and fault flip-flops (30a-b). Improved circuitry for controlling the writing to the BAMs includes a timer ("BAM-protection timer") (40) coupled to the write-enable input of each of the BAMs. The BAM-protection timer has a trigger input (43) coupled to the microcomputer. The microcomputer is programmed to execute an instruction to generate a triggering signal at the BAM-protection timer's trigger input immediately prior to executing an instruction to write to the BAM. This opens a window for writing; the duration of the window is set to be just long enough to allow the completion of the write operation. The fault flip-flops, once set, unconditionally prevent writing to the BAMs, regardless of any other signals that might be present. The setting of the fault flip-flops is controlled by a first timer ("watchdog timer") (60) and a second timer ("second-chance timer") (62).

Abstract: Method and apparatus for the improved operation of an electronic computing scale provides significantly increased resolution in a first weight sub-range (0-12 pounds in the illustrative embodiment). A coarser resolution is provided in a second weight sub-range (11-100 pounds). The raw load cell voltage is communicated along first and second branches, and subjected to a different transformation in each branch to produce first and second transformed voltages. In the first branch, raw voltages corresponding to weights in the low sub-range are mapped onto a desired sub-range of voltages. In the second branch, raw voltages corresponding to weights in the high sub-range are mapped onto a second sub-range of voltages. Depending on the weight on the scale, one or the other of the transformed voltages is applied to the ADC input terminal, and the digital output is scaled accordingly. The circuitry includes a range flag and logic circuitry for sensing the digital ADC output, and controlling the range flag.

Abstract: A postage meter stepper motor module for use in a postage meter of the type having a base supporting a rotatable main shaft to which a printhead is mounted. The main shaft has a number of value rods mounted to it. The outer ends of the value rods are coupled to the printhead so movement of the value rods parallel to the main shaft axis changes the chosen value print character at the printhead. The stepper motor module includes a stepper motor frame mounted to the base at a chosen position relative to the main shaft. A stepper motor is mounted to the stepper motor frame. A yoke couples the stepper motor to a chosen axial position along one of the value rods through a coupler ring. The coupler ring and yoke allow the value rod to rotate freely about the main shaft while maintaining the axial position determined by the stepper motor. The stepper motor and yoke are coupled by a rack and pinion arrangement to translate the rotary motion of the stepper motor to the linear motion of the yoke.

Abstract: A shaft assembly, including a main shaft, is used with a postage meter of the type including a base supporting the main shaft. A printhead is mounted to the outer end of the main shaft so the main shaft and printhead rotate together. The main shaft has a flat surface against which a number of elongate value rods are mounted parallel to the main shaft axis. The outer ends of the value rods are coupled to the printhead to operate the printing elements of the printhead. The inner ends of the value rods are connected to stepper motor drives, mounted to the base, to move the value rods axially. Bearings, mounted to the main shaft, radially position the main shaft relative to the base. At least one of the bearings is fixed to a chosen axial position along the main shaft so that such bearing, when mounted to the base, also axially positions the main shaft relative to the base.

Abstract: A printhead assembly is used with a postage meter of the type having a base supporting a main shaft and a stepper motor drive. The stepper motor drive positions value rods carried by the main shaft according to the value of the postage to be printed. The printhead assembly includes a value module mounted to an outer end of the main shaft so to rotate with the shaft. A dater/slogan module is also mounted to the outer end of the main shaft assembly and is positioned or indexed, such as using guide pins, to the value module. The components are housed within an enclosure including a separate printhead cover assembly. The printhead cover assembly includes an opening through which the field service personnel has access to the dater/slogan module to allow the them to remove the dater/slogan module, such as for maintenance or repair, without affecting the security of the meter.

Abstract: A cover assembly for use with a postage meter includes an upper cover having a display opening and a keypad opening formed in one side. The upper cover is secured to a lower cover to provide a housing or enclosure for the meter. A display assembly, including a character display, and a keypad are both mounted to the inner surface of the upper cover. Portions of the keypad extend through the keypad opening while the character display is visible through the display opening. A support plate is mounted to the underside of the upper cover and is shaped to generally conform to the shape of the contents beneath the cover. The support plate is configured to press against the keypad and display assembly so to secure them in place. A battery, used to power the meter when removed from the meter base, is also supported between the support plate and the upper cover.

Abstract: A modular universal postage meter includes a base to which stepper motor modules and a drive shaft assembly are mounted to predetermined positions relative to the base. The drive shaft has a bifurcated printhead, including a secure value module and a field service accessible and removable dater/slogan module, mounted to its outer end. The stepper motors are coupled to the value module of the printhead through a number of value rods mounted to and parallel with the shaft assembly. The value rods can move parallel to the axis of the main shaft. Rings surround the shaft engage respective value rods and are themselves axially positioned by yokes coupled to the stepper motors. Since the stepper motor modules are registered to the base, they can be moved and replaced with minimal adjustments and realignment since the shaft assembly is likewise registered to a predetermined position relative to the base. Thus the base acts as a reference for the stepper motor modules, the shaft assembly and the printhead.

Abstract: A microcomputerized postage meter that provides high degrees of security and fault tolerance. The meter maintains data security under low power conditions by the use of functionally nonvolatile memory units. Register and other data which must survive normal and abnormal losses of power to the meter electronics are stored in dual redundant battery augmented memories (hereinafter designated BAMs). Upon detecting an error condition, the microcomputer writes an appropriate fault code to the BAMs. A mechanism for disabling the meter includes dual redundant flip-flops which are set to a "faulted" state upon detection by the microcomputer of a failure condition. These flip-flops are powered by the BAM batteries. They cannot be reset except by physical access to the meter interior, which access is only available to authorized personnel at the factory. The fault flip-flops are also set when the microcomputer fails to properly execute its own operating program.