GSM modem series now supports output switching based on DCD signal
07 May 2009
Insys Microelectronics has updated its popular GSM Modem Series to include the switching of an output when the communication Data Carrier Detect (DCD) is set. This new feature ensures a superior interface between PLC and modem allowing better control and integration, especially for logic controllers and RTU devices without full modem control serial ports.
In practice many logic controllers and devices don’t support full serial data lines such as Data Carrier Detect (DCD). The DCD line is turned ON when the DCE (modem) is receiving a signal from a remote DCE (modem), which meets its suitable signal criteria. This signal remains ON as long as there is a connection between the two modems indicating a safe condition. If the controller cannot detect a DCD signal via the serial port, it is blind to the status of the communication link.
This new output is connected to an input of the logic controller or RTU which can then be programmed to take appropriate action on loss of signal. An example of this could be that the controller switches to an alternative communication link or safely closes down the application or process. The DCD signal can also allow for switching the logic controller or RTU from ’data’ mode to SMS mode to support the sending of SMS messages from the application.
Insys GSM Modem Series are Industrial DIN-rail mounted devices that communicate over the GSM cellular mobile network. They appear like a common modem to the logic controller or RTU application.
The INSYS GSM 4.2 comprises simple data communication, alarm and security functions. Alarms with a user defined text – e.g. as an SMS message – are triggered by digital inputs. The digital outputs can be controlled remotely by SMS, by DTMF (tone dial telephones) or over a data connection. They can be configured to display an alarm status as well. Selective call answer allows only data calls from specified numbers, thus ensuring a level of security.
The INSYS GSM 4.2 is also available as a slim-line design; the INSYS GSM 4.2 Compact. Two special versions in the INSYS GSM Series have specific functions and interfaces to the Siemens LOGO! and the Moeller EASY .
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