Abstract: A method and apparatus provides for, as a part of call setup and routing whenever a calling party calls a called party, which includes determining a local time for the called party prior to completing call setup. If the local time is within a specified time range, a message is played to the calling party to advise the calling party of the local time for the called party. In one embodiment of the invention, the calling party is given the option of leaving a message or of continuing with the call in the case of an emergency. The message delivered to the calling party may be one that is generated by an interactive voice response unit or by a short message service server. In either case, based upon the calling party's response to the message, the inventive method and apparatus result in the cellular network either taking a message for the called party or routing the call to the called party as normal.

Abstract: Voice-band modems are used to transmit information via a loaded telephone line when a telephone connected to the line is on-hook. When the telephone is off-hook, the integrity of the line is checked by transmitting a pilot tone from the subscriber end to the central office end of the line, where the pilot tone is monitored. Filtering of pilot tones in the central office is avoided by using two different pilot tones for originating and answered calls. An alarm condition at the subscriber produces a shifted pilot tone frequency. Loss or a change in frequency of the monitored pilot tone causes a telephone call on the line to be temporarily interrupted for checking the line and alarm condition. The central office and equipment can be switched to poll consecutively a plurality of telephone lines.

Abstract: An imput of a CMOS integrated circuit device is protected from excessive voltage swings at an input terminal by a protection circuit which comprises two series-connected protective stages between the device input terminal and the input. Each protective stage comprises a current-limiting series resistor and clamping diodes connected to the supply voltages of the device. The two stages enable the series resistance of the protection circuit to be much lower than that required for a single stage diode clamping arrangement, this being particularly advantageous if the device is an analog-to-digital converter for converting to digital values analog voltages present at the input terminal.

Abstract: An analog signal is sampled in response to a sampling command. Each time that the analog signal, or the difference between the analog signal and the previous sample thereof, crosses a respective reference level, a digital signal is produced. Each digital signal consists of a code representing the level crossing or incremental change in level which has occurred and a count representing the time which has elapsed since the last sample command. A digital signal is also produced if the elapsed time reaches a predetermined period. On production of each digital signal, a sampling command is produced and the elapsed time counting is recommenced. The digital signals constitute a digital representation of the analog signal. The converter is particularly useful for converting analog signals having both very high and very low frequency portions, such as current surges which occur on telephone lines affected by lightning (high frequency) and 60 Hz induction (low frequency).

Abstract: A guidance system suitable for use in burying cable uses a previously buried signal-emitting cable to produce a signal along the cable path. A vehicle mounted plow used to plow a second path has a receiver which analyzes signal from the buried cable and determines from it both the lateral direction and the extent of vehicle movement in order to maintain a predetermined lateral spacing of the two paths.