Calta Computer, manufacturer of Mdbus (Modbus for Windows), PLC09 Arbitrator

Calta Computer Systems Limited



Our company was incorporated in April 1981. Initially Calta provided custom solutions to a wide range of data communications applications. From these applications emerged a common set of requirements leading to the development of the product family described below. Today our focus is the supply of our standard products augmented by custom additions where dictated by unique customer requirements.


This device permits a single ported PLC or other remote device to be connected to up to three Hosts. The device was designed for use with Allen-Bradley Full or Half Duplex DF1 communication. In addition to the multiplexing aspect, the unit provides RTS control.

Note! - A time limited fully functional demo copy is available.
Click here to request a copy.

Order - Standard Mdbus $180 USD, Standard+OPC Mdbus $230 USD
To Order

Dnbus is a software package running under Windows that implements the MODBUS subset used in Daniel Industries 2500 protocol and has much the same features as Mdbus. In addition it is capable of polling for Archive data and storing it in Excel via DDE.

Note! - A time limited fully functional demo copy is available.
Click here to request a copy.

This device provides a cost effective solution for the addition of a Modbus RTU Protocol port to an Allen-Bradley PLC5. The standalone PLC09 Converter communicates serially (ie. using Channel 0) with the PLC5. Mapping configuration information (Modbus registers to PLC5 files) is contained in an ASCII file which can be downloaded to the PLC09 via a dedicated serial port. In addition, the PLC09 provides another serial port which allows transparent sharing of the PLC5 port with another Host using DF1 protocol.

View the Modbus to DF1 Converter Operator's Manual in PDF format

This device converts between different serial asynchronous protocols. By front ending foreign devices with the PLATOR they can be easily integrated into existing systems. A standard converter exists for MODBUS to Foxboro 760.


Occasionally our standard product offerings do not meet a unique customer requirement. These unique applications can usually be serviced by incorporating the required special features into our standard product. Please contact us with your unique communications requirements.

  • We have used both custom and standard communication drivers in conjunction with Microsoft Access and Microsoft Excel to produce custom Operator Interfaces. These packages produce a very cost effective interface for many applications.

Send E-Mail to Calta Computer Systems (

Skype - lorne.schneider

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Twitter - @caltacomp

We can also be contacted as follows:

Calta Computer Systems Limited       Phone - 403-252-5094 
452 Oakwood Place SW    
Calgary, Alberta, Canada             Attention: Lorne Schneider, P. Eng.
T2V 1R6                                         Sydney Deitch, P. Eng.