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Product Description

The Model 122 is a dual card mounted version of the Model 285 except that the operating speed for the converter circuitry of the Model 122 has been increased to 115.2 KBPS. The interface converter circuitry of the Model 122 can be configured to operate in compliance with RS-485 or RS-422 equipment and RS-232. When operating as RS-485 the Model 122 has an intelligent mode which provides control of the RS-485 line. When configured to operate as an RS-232 to RS-422 interface converter, the Model 122 converts between full duplex data, TD and RD, between RS-232 and RS-422.

As an RS-232 to RS-485 converter the Model 122 can be configured as a 2 wire or a 4 wire converter . Since RS-485 is a half duplex protocol, the Model 122 can be configured to control it’s data flow in one of two ways. The first is via the use of RTS, pin 4, of the RS-232 port. In this case the RS-485 transmitter will turn on when RTS is turned on. When RTS is off the Model 122 is in the receive mode.

The second method of controlling the RS-485 transmitter is to turn it on when TD data is applied to theRS-232 port. The receiver also operates differently depending on whether the mode is two or four wire. In the two wire mode when no data is received by the RS-232 receiver the RS-485 receiver is switched on. In the four wire mode the RS-485 receiver is constantly on while the transmitter is switched as required.

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