RS-232 4-Channel DPDT Relay Controller problem

We ordered 3 RS-232 4-Channel DPDT Relay Controller with Serial Interface

We encountered a problem with 2 of them in our testing. (The 1 other working well)

We trying to connect with no success and without the ability to toggle the Relay’s.

Do you familiar with that problem?


It’s unusual for two of the boards to not work.

I believe you’re referencing this product:

Are you using this with a USB adapter?
Are the jumper settings the same for all three devices?
When the non functioning devices are connected do they display as a serial port?
If you are using it with a USB adapter can you check that the PC/MAC jumper is set to MAC?