Abstract: A circuit and method for determining connection status of a phone line shared by multiple telecommunications devices, such as modems and phones, are provided. The phone line includes respective tip and ring lines. The circuit comprises a first operational amplifier coupled to receive a signal indicative of a voltage difference between the respective tip and ring lines. The circuit further comprises a lag network coupled to impart a predetermined delay to the output signal from the first operational amplifier. A second operational amplifier is coupled to receive the voltage difference signal. The output signal from the second operational amplifier has a sufficiently fast time response relative to the output signal from the lag network.

Abstract: An asymmetric-rate communication method and system for remote data collection using a processor-operated modem at a respective data collection site is provided. The modem processor used at the data collection site may be rated to have a predetermined relatively low processing power. The method includes a first selecting step that allow for selecting a first protocol for transmitting data at a predetermined rate. The selected first protocol uses a predetermined percentage of the processing power of the processor. The method includes a second selecting step that allows for selecting a second protocol for receiving data at another predetermined rate. The selected second protocol uses another predetermined percentage of the processing power of the processor.

Abstract: A correlator for identifying global positioning satellites includes an antenna at a central location for receiving signature signals from a plurality of the satellites. Each received signal is converted from analog to digital form. A filter is employed to correlate each digital signal with a respective, unique code sequence. Each filtered digital signal is supplied to a circuit which produces an indication that identifies each satellite from the filtered digital signal supplied to the circuit.