# What is an Autodialer/RTU?

The Catalyst RTU (Remote Telemetry Unit) functions as an auto-dialing remote alarm monitor and data logger. Auto-dialers and RTUs are typically used at remote, unattended locations, to monitor the condition of automatic equipment. The mission of an Autodialer/RTU is to compare inputs against alarm criteria. Then if alarm violations occur, the RTU calls maintenance personnel (or a central station computer) to inform them of the "out of normal" condition at the remote site. Alarm notification reports are typically made to operators as voice reports. However, data reports to central computers can be made as well.

All user programming configurations, including recorded messages, are maintained in permanent non- volatile flash memory within the product. This information can also be stored on a local hard disk with the use of Alarmware™.

The Catalyst RTU incorporates extremely thorough and effective electrical surge protection, as well as overall rugged construction, to deliver reliable operation under real-world conditions.

The RTU may be factory equipped with different input and output options. Inputs and outputs are known to the RTU as Channels. In the Catalyst RTU channels are of two classes: Physical Channels and Industrial Network Channels. The RTU can input data from, and output data to, channels of both classes - physical and industrial network. Furthermore, both physical and industrial network channels can be of two data types - discrete and analog.

Physical Channels are channels whose input and output circuitry is physically a part of the RTU hardware. Physical channels are monitored and controlled directly by the RTU microprocessor hardware. The connection between the RTU and its physical channels cannot be broken. So they will never cause communications failure alarms, or, be unable to access channel data.

Industrial Network Channels are channels that are not physically a part of the RTU hardware. In fact, the RTU may access Industrial Network Channels that 1) physically reside in several different units simultaneously, 2) are located in different types of equipment, 3) may be from many different manufacturers, and 4) may even be located not in close proximity to the RTU.

Industrial Network Channel data is monitored and controlled over industrial networks. Industrial networks are usually, but not always, serial data communications interfaces. Common types of industrial networks are Modbus, ModbusTCP, and Allen-Bradley DH-485, or EthreNet/IP.

The most common type of device interfaced to the Catalyst RTU via an industrial network is the Programmable Logic Controller (PLC). Data in a PLC resides in its data table. Individual locations in the PLC data table are called data registers. Data registers can represent inputs, outputs, general-purpose memory, and PLC status points. Almost any data register in a PLC can become a channel to the RTU.

Industrial network channel data is kept current by the RTU continually scanning (making queries to) PLC data registers. However, unlike physical channels, industrial network interfaces may get interrupted or broken and may become congested by network traffic. Therefore, industrial network channel data may become inaccessible. Industrial networks that become inaccessible can cause communications failure alarms.

When a channel's configured alarm violation condition occurs and persists for the programmed Alarm Trip Delay time, the channel goes into an Unacknowledged Alarm state, and the RTU begins the process of communicating with designated destinations to deliver the specific alarm information.

The most common type of Destination is telephone numbers, to which the product places alarm calls and delivers specific corresponding voice messages which the user has pre-recorded to identify the exact nature of the alarm condition. However, destinations can also include other items, such as an output to a local serial printer via a serial port, etc.

The process of alarm notification continues until a proper acknowledgment has been received by the RTU.

Certain special "global" events not associated with any particular channel can also cause alarms. Examples are; interruption of primary power to the product, which would cause a power failure alarm, or failure of industrial network interfaces to PLCs, which would cause a communications failure alarm.

Delivery of the alarm message may be in the form of a voice call directly to personnel, as described above. Alternatively, calls may be made in data mode. With data mode calls, the product establishes modem communication with a called device for the purpose of transmitting information in a non-voice data format.

The RTU can also be programmed to take data samples ("snapshot" readings) from its active channels on a regular interval basis. These channel data samples are kept in the RTU log file and written to the local data logger (printer). The RTU can be called for retrieval of log file data by a central station computer. The burden of retrieving data logs is generally on the operator of the central computer. However, a configurable parameter of the RTU called the "high-water mark" allows for RTU initiated automatic transfer of logged data to the central computer, should the log file approach overflow before the central computer calls the RTU.

Input channels may also optionally be configured to export their contents to specific Destination Network Addresses (DNA). This function can be used to link one point in a network to another point. This export process refreshes at the scan rate of the industrial networks involved in the transfer process.

Note: DNA are not to be confused with destinations, to which reports are delivered only under certain conditions such as an Unacknowledged Alarms.