diff --git a/scripts/spt25.gd b/scripts/spt25.gd
index 965445b..b00b420 100644
--- a/scripts/spt25.gd
+++ b/scripts/spt25.gd
@@ -13,6 +13,32 @@ class SPT25 extends unit.Unit:
 
     func _to_string() -> String: return String('СПТ-25 %s %s' % [self.name, ['отключен', 'на связи'][int(online)]])
 
+    ##Вычисление контрольной суммы
+    func sciCalcFCS(src: PackedByteArray) -> int:
+        var P_DIV = 0
+        var ln = src[0]
+        var FCS = ~((src[2]<<8) + src[1])
+        for i in range(3, ln):
+            var C = src[i]
+            for j in 8:
+                if C & 1:
+                    if FCS & 1:
+                        FCS = ((FCS >> 1) | 0x8000)^P_DIV
+                    else:
+                        FCS = ((FCS >> 1) | 0x8000)
+                else:
+                    if FCS & 1:
+                        FCS = (FCS >> 1) ^ P_DIV
+                    else:
+                        FCS = FCS >> 1
+                C >>= 1
+            for j in 16:
+                if FCS & 1:
+                    FCS = (FCS >> 1) ^ P_DIV
+                else:
+                    FCS = FCS >> 1
+        return ~FCS
+
     func _init(nm) -> void:
         self.name = nm
         tx_data.resize(8)