if (!element_len) return -1;
int decode_symbol(unsigned char *element, int element_len) {	// 0x18 Map Symbol - Packed 4-bit integers	int c;	if (!element_len) return -1;	lprintf(T_OPENTRAC, "Symbol: ");	for (c=0;c<element_len;c++) {		if (c>0) lprintf(T_OPENTRAC, ".");		lprintf(T_OPENTRAC, "%d", element[c] >> 4);		if (element[c] & 0x0f) lprintf(T_OPENTRAC, ".%d", element[c] & 0x0f);	}	lprintf(T_OPENTRAC, "\r\n");	return 0;}