Abstract: A telephone switch in which communication between tasks controlling the switch hardware and the timing of those tasks, including the timing of repeating tasks, is controlled through a mail system in which mail messages are sent between tasks that may be running on separate microprocessors. The mail messages specify the destination task, the function that the task is to perform and any desired delay before the mail is to be delivered to the destination task. Repeating tasks send mail to themselves each time they repeat, specifying in the mail message the task to be repeated and the desired delay interval. A mail task holds the mail for the specified delay interval before it is delivered, and receipt of a mail message causes the task to run.

Abstract: A multiple-RF channel wireless security system has expanded monitoring and control capacity without a concomitant increase in the number of available RF channels. At least one primary condition-responsive monitoring and RF signaling device having a first range of values for the parameter being monitored has an associated secondary condition-responsive monitoring device having a second range of values for the same parameter connected in series with the primary device. The secondary device may operate in conjunction with or independently of the primary device. When operating in conjunction with the primary device, the secondary device supplements the primary device by providing a second range of parameter values, and may, for example, provide back-up or "fail safe" operation of the primary device. When operating independently of the primary device, the secondary device provides expanded monitoring and control capabilities of the security system while preserving the number of RF channels.