Baud rate

For a proper '62 experience, one should use the same baud rate for communicating to modem as the modem uses to communicate with the other modem, that is 300 baud. Fortunatelly, the microcontroller supports such low baud rates, but the problem is the Serial-USB bridge, that might be not capable. So, one needs to make sure the bridge is able to handle such speed.

For example, CH340, as the one found in cheap Chinese clones of Arduino Nano v3, works perfectly.

Of course, the DCE-DTE speed might be much higher, like 1200 or 9600 baud. In this case, flow control has to be enabled and supported by the Serial-USB bridge and the communication software.