diff --git a/library/CBSP_Types.ttcn b/library/CBSP_Types.ttcn
index c4c6cf2..5ab3c98 100644
--- a/library/CBSP_Types.ttcn
+++ b/library/CBSP_Types.ttcn
@@ -378,5 +378,24 @@
 external function dec_CBSP_PDU(in octetstring msg) return CBSP_PDU
 	with { extension "prototype(convert) decode(RAW)" };
 
+/* convert from warning period encoding to seconds */
+function f_cbsp_period2s(uint8_t period) return integer
+{
+	if (period == 0) {
+		return -1; /* infinite */
+	} else if (period <= 10) {
+		return period;
+	} else if (period <= 20) {
+		return 10 + (period - 10)*2;
+	} else if (period <= 38) {
+		return 30 + (period - 20)*5;
+	} else if (period <= 86) {
+		return 120 + (period - 38)*10;
+	} else if (period <= 186) {
+		return 600 + (period - 86)*30;
+	} else {
+		return 0;
+	}
+}
 
 } with { encode "RAW"; variant "FIELDORDER(msb)" }