Abstract: A microprocessor fault logging arrangement includes a detector for detecting hardware and software faults 3, 4, 8, which produce an interrupt signal which is applied to the non-maskable interrupt input NMI of microprocessor 1 and, which is also applied via delay circuit 5, to the RESET input of microprocessor 1. The NMI input causes microprocessor 1 to store the state of selected system parameters in a log of fault records stored in a non-volatile memory 2, the selected parameters being stored for fault analysis each time an NMI input signal is generated interrupt signal is applied to the NMI input. The delay circuit 5 allows sufficient time for the selected parameters to be stored in the non-volatile memory 2 before the microprocessor is reset.

Abstract: A line switch control circuit for a telephone subset comprising a line switch (2), a hook switch mode detector (TR4), a voltage sensing circuit (TR5) having at least two inputs (D and F), and a dialler chip (3) having a CMOS push-pull pulse output (DP). The circuit ensures that when the subset is in the on-hook mode, on the one hand, an appropriate level of current is drawn from the exchange line (L1, L2) to energise the dialler chip (3), and on the other hand, the line switch (2) remains non-conducting during on-hook mode.In the off-hook mode, the circuit renders the line switch non-conducting during breaks in dialling signals as well as during flashes by diverting current from the line switch into the pulse output (D) of the dialler chip.

Abstract: A system for monitoring use of a utility at a consumer's premises is disclosed. The system may include monitoring apparatus to detect use of the utility, a first register to store an indicator signal indicating whether or not use of the utility at the consumer's premises is authorized, and an unauthorized use signal generator, responsive to the monitoring apparatus output and the contents of the register, to generate an unauthorized use signal when the monitoring apparatus output indicates use of the utility and the first register contains an indicator signal indicating that use is not authorized.