A try/ catch debug statement around your code would have shown you errors that variable 'A' is not defined.

Extender 'A' is hexadecimal representation of extender ID. Character A is treated as a variable and not as a number.

Serial ports are referenced using 0 to 3.

var e = CF.extender[10]; // or [0x0A]
var s = e.serial[1];

This will reference Serial Port 2 on Extender A.

Note that every time you send to an extender port, the receive buffer is cleared so using RS232 to constantly receive events from equipment is problematic.

I know there are threads about this that I authored long ago. Search for 232 and UART and you can read up about it. IIRC, those were the keywords.

From what you are sending, you are talking with a Marantz or Denon unit. I'd highly recommend using TCPIP to port 22 vs doing the RS232 way.