Abstract: This invention is directed to a memory card assembly having a first end connected to a host device and a second end connected to a retractable antenna assembly. The memory card assembly includes a radio for two way communications between the host device and a remote location. The antenna assembly comprises a housing for two antennas and two light emitting diodes (LEDs) that indicate the status of the radio. The two antennas and the two LEDs are connected to the memory card circuit board through two dual function connectors that concurrently pass analog and digital signals.

Abstract: A communication system that provides dual frequency communication using a single superheterodyne receiver that receives both the desired frequency and the image frequency of a transmitted signal. If communication cannot be established on a desired frequency, the transmitter switches to the image frequency while the receiver frequency remains constant.

Abstract: A bar code scanner employs a digitizer for the signal produced by a photodetector in response to light reflected from a bar code symbol. The digitizer uses a first derivative of the signal to detect peaks, and determines the amount of movement of the signal after each peak to see if a threshold amount of movement has occurred. A second derivative of the signal is used to detect inflection points, and when one occurs after the threshold amount of movement following a peak, a valid transition of the signal is signalled. These valid transitions are decoded to recover the bar code pattern. The threshold used is adjustable to optimize the digitizing for different types of bar code symbols and other conditions, or to provide a squelch function. Dynamic control of the threshold provides a varying response to the scanned bar code symbol. Zero-crossing detectors used with the first and second derivative circuits may also have variable thresholds.