NSString format & xtra characters

[Dreamspinner]

I'm trying to send an ASCII string with CRLF appended, to a device via a serial port.

NSString *sendString = [[inputTextField stringValue] stringByAppendingString:@"\n\r"];

//[inputTextField stringValue] is "AP1090;".	

if([self.port isOpen]) { // in case an error occured while opening the port
  [self.port writeString:sendString usingEncoding:NSUTF8StringEncoding error:NULL];
}

When looking at the value of sendString in the debugger it shows:

sendString	__NSCFString *	0x0000000101917800@"AP1090;\n\r\x0e\x19\x10"

What are the extra characters "x0e\x19\x10" and are they supposed to be there?

The device is not responding.