Remote Terminal Unit Glossary

Alarm Master
An alarm master is the core of a monitoring system. An alarm master collects alarms from remote telemetry units (RTUs) and displays them for one or more operators.

Analog inputs
Primarily found on an advanced remote terminal unit. An input that accepts a continuous range of states from an analog sensor of some kind, such as temperature or humidity.

Control relays
A control relay is a switch on a remote terminal unit that another device may be wired into to achieve remote control of that device. Typically used to activate generators, unlock doors, without having to travel to the site.

Derived controls
Derived controls apply rule sets to incoming alarms to control complex automatic responses to emergencies. There are two types of derived control: echo and formula.

Discrete alarm inputs
Found on a remote terminal unit. An alarm input that can be one of only 2 states: Alarm or Clear.

Ping alarm
A ping alarm is an automatic alert sent to you when one of your LAN connected devices fails to respond to successive pings. Modern alarm monitoring equipment, such as a remote terminal unit, can be configured to send scheduled pings to a large number of devices every few minutes (some remote terminal units support ping alarming to as many as 32 distinct IP addresses simultaneously.

Programmable Logic Controller (PLC)
A programmable logic controller is a digital computer used for automation of industrial processes, such as control of machinery on factory assembly lines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. PLCs are typically considered the equivalent of a remote terminal unit in production SCADA environments. They do, however, suffer from much lower point capacities and reporting capabilites.

Proxy agent
An SNMP agent that translates non-SNMP messages and inputs to SNMP. In network alarm monitoring, a proxy agent is usually a remote terminal unit that converts contact closure inputs to SNMP traps, like the NetGuardian 832A.

Scripts
Small programs that are put into a remote terminal unit to perform simple tasks.

SNMP agent
SNMP agents expose management data on the managed systems as variables (such as "free memory", "system name", "number of running processes", "default route"). The managing system can retrieve the information through the GET, GETNEXT and GETBULK protocol operations or the agent will send data without being asked using TRAP or INFORM protocol operations.

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