A device for alerting network administrators to network problems. Some vendors use the term “data alarm” to describe a device that senses network problems associated with the flow of data.
These devices typically monitor serial lines such as RS-232 connections for the presence or absence of certain signals. For example, you can monitor the connection between a print server and its attached printer or between an access server and a modem or a Channel Service Unit/Data Service Unit (CSU/DSU).
A data alarm can be a simple device that monitors one serial line for the presence or absence of data. If the data flow stops, a flashing LED or audible alarm signals the problem to the administrator. More complex data alarms can support multiple serial lines or other serial interfaces such as RS-449 and V.35, can have programmable functions and menu-driven commands, and can monitor other devices, such as Time to Live (TTL) devices. These more complex devices can be configured to dial a remote station when a problem arises and to generate a report of the condition or even activate an alphanumeric pager.