E2A Glossary

Address

An ID that uniquely identifies a particular E2A device. Each command includes this address information, so each remote device knows when it is to respond. Even though remotes may see commands, they will not respond unless the address matches. This is key to any polled protocol, to avoid collisions when multiple remotes share the same circuit.

Alarm Point

A single bit that identifies a specific condition or status.

Alarm Polling

The most common & fastest type of E2A polling, where the E2A master requests the remote for its status summary. The most useful pieces of information are weather or not there are new alarms in the remote or if any alarm are currently standing in the device.

Alarm State

Whether the alarm point is currently failed or cleared.

Communication Circuit

A communications path between an E2A master and the alarm remote(s). Typically this takes the form of a voice channel, with 202 modems. 202 modems run at 1200 baud and are slow by today's standards.

Controls

The E2A protocol allows NOC's to send commands to remotes that effect the device. In case of alarm remotes, this typically closes a relay. In case of other device, these command can alter the current operating parameters of the device. The E2A protocol supports Operate & Release commands as well as momentaries. Latch commands, will hold a relay until such such time that relay is released (Like a light switch). Momentaries will energize a relay for a few seconds, and then release it (Like a push button)

Display

A group of 64 points. Displays can be requested by the E2A master on an individual basis. E2A has 64 displays, though only 60 are usable starting from display 5. The first 4 displays are reserved for internal use.

E-Telemetry

Generic name for devices or masters that use the E2A protocol

Group

Some E2A devices, request alarms by group number instead of display number A single group request from an E2A master, can report up to 4 displays.

Passive Monitoring

The ability of DPS alarm master stations, such as the T/Mon NOC, to watch both commands from another E2A master and responses from the alarm remotes and process those responses as though it had sent the command. If passive systems detect lack of polling activity, they can assert control of the line and commence active polling of the network.

Polling Leg

A group of Remotes that are reporting to the same communication link to a single port of the E2A master. Its not uncommon for a NOC to support several polling legs. When possible to do so, splitting devices into multiple polling legs, will allow you system to collect data faster and reduce the effect of a single circuit failure.

Polling Loop

The act of the alarm master, collecting alarm information, on an address by address basis until all devices has been polled once. This is also known as "round robin" polling, because once one polling loop is complete, the sequence repeats over and over again.

Variable Group Size

Some devices that use group polling, only output some subset of the 4 display maximum.

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