The ST23 CPU has employed an Industrial Standard Microcontroller Based System (Motorola MC68HC111) designed specially for low power consumption from a large, reputable manufacturer.

Industrial Microcontroller shall be preferred over desktop PC microprocessors as they have a longer manufacturer support life span. The micro-controller used shall be available off-theshelve from Malaysia market without proprietary software or firmware embedded.
 

Dual Watchdog Timers are provided to automatically reset the system in the event of system software or hardware failures. The 1st watchdog timer generates a soft internal reset of the CPU and has a time-out of less than that of the 2nd. The 2nd watchdog timer are configured to provide a hard external reset of the CPU.
 

A Real-Time Clock/Calendar (RTC) has been provided to keep accurate time and date information of events. The clock employed allows synchronization to external time signals provided by the Centre Monitoring Station or from the GSM network. The RTC has an internal, battery-backed RAM capable of retaining data for 10 years without external power. The Real-Time Clock is Year 2000 compliant.
 

Data Acquisition can be divided into two broad classifications – Real Time data acquisition and Data Logging. Remote Terminal Unit (RTU) normally related to Real Time data acquisition is when data acquired from sensors is used either immediately or within a short period of time, such as when controlling a process. Normally real time data is tagged with date/time at Master Station.

Data Logging is a method of data acquisition when data acquired from sensors is stored in memory for later use. Data Logger measure sensors at a specific scan rate, process data, store the data in final storage, and initiate telecommunications or waiting for retrieve activity. Normally all logged data is tagged with date/time either directly or indirectly.

The ST23 RTU controller is designed with both real-time data acquisition and data logging features. Up to four (4) sensor parameters can be logged into each record with the date and time stamp for the data.
 

The ST23 is capable of receiving user-initiated SMS, transmitted from maintenance personnel mobile phone, to request for Real-time Hydrological Data. The command SMS is password protected to prevent unauthorized personnel from requesting the SMS data, which may cause the RTU mobile phone bill to be high.

Real time data can also be retrieved by simply by issue a call to the RTU mobile number, the RTU will drop the call without answer to it to avoid any Call Charges. This function is called "Missed Call". Upon receive the request command, the RTU will reply the latest data in the RTU memory the Caller.
 

The ST23 is capable of receiving user-initiated or automatic control command signals, transmitted from the CMS or another RTU, to actuate external device such as pump control, warning sirens, or control valve when is required later. The ST23 installed at the hydrological station can be programmed to send control commands in form of SMS straight to another ST23 installed in a Flood Warning Siren Station to operating the Siren remotely.

Any transmitted commands signal will be sent immediately, independent of any preset communications interval.
 

Equipment deployed externally in the Malaysian environment may encounter lightning surge problems during heavy thunderstorms. The ST23 RTU is designed with lightning surge protection on the signal input line and power supply input.