Honeywell third-party communication

Thread Content

I am not a DCS technician; our plant’s DCS system communicates with third-party devices via S7-200. 1. The DCS system is fully configured without any issues; it has been used before as well. 2. The S7-200 was without power for approximately 1.5 years, and the voltage at the communication line was 3V. “The communication cables are not labeled, and the communication terminal blocks are also unlabeled.” 3. There are two communication switches; none of the channels are numbered, so it’s not clear which channel was used previously. The communication twisted pair is in good condition, with a wire resistance of 2.6 ohms. Each channel was connected with the positive side on the left and the negative side on the right; none of the TX and RX lights on the switch lit up. When the wires were connected with the negative side on the left and the positive side on the right, only the RX light turned on for each channel. 4. DCS communication with third parties was attempted; when connected in the left-positive/right-negative configuration, no communication was possible, and none of the lights on the switch lit up; testing with the connections reversed was not carried out. 5. What are the main reasons why the TX and RX lights do not light up in the \"positive on the left, negative on the right\" connection method? “In a “left negative, right positive” communication cable, only one light is on – how does this situation occur? Reconnect the communication cable and then activate the DCS channel. Due to a lack of experience, I’m not sure if this method will work; could reconnecting the communication cable affect the switch ports?