Improve explanations for DP0* callsigns

references/Hilfsmittel.md

@@ -55,7 +55,9 @@ those are memory items.
 - **S. 5 — Tabelle "Rufzeichen mit 2- oder 3-buchstabigen Suffixen":**
   the main **call-sign-series → class/use** table. DA0 = Klubstation;
   DL1–DL9 = person-bound class A; DO1–DO9 = class E; DN9 = class N;
-  DP0–DP1 = exterritorial class A; etc.
+  DP is intended for exterritorial-location call signs; DP0–DP1 =
+  class A with use categories KS, RL/FB and SZ; DP2 = class E with the
+  same use categories; DP8 = class N with the same use categories.
 - **S. 6** — club-station suffixes (1-char) table.
 - **S. 7** — club-station suffixes (4–7-digit); **§ 5** Kurzzeitzulassungen
   ausländischer Funkamateure (visitors in Germany sign **DL/** class A,