private static final byte []
checkAndConvertAddress(String address) {
	int length = address.length();
	byte [] out = new byte [length];
	for (int i = 0; i < length; i++) {
		char c = address.charAt(i);
		if (!Character.isDigit(c))
			return null;
		out[i] = (byte) c;
	}
	return out;
}
X25 - identifies the PSDN (Public Switched Data Network) address in the
X.121 numbering plan associated with a name.

@author Brian Wellington
src/main/java/core/org/xbill/DNS/X25Record.java