diff --git a/src/simpleframes.ts b/src/simpleframes.ts
index 9a55fda..c76b557 100644
--- a/src/simpleframes.ts
+++ b/src/simpleframes.ts
@@ -4,25 +4,24 @@ import {MeterbusLibUtils} from './utils'
 export namespace MeterbusLibFrames {
     export abstract class Frame {
         protected _telegram : number[]
-        protected _startCharacter : number
-        protected _frameLength : number
-        protected _firstPayload : number
-        protected _payloadLength : number
+        protected __startCharacter : number
+        protected __frameLength : number
+        protected __firstPayload : number
+        protected __payloadLength : number
 
         constructor(startCharacter : number, frameLength : number, 
             firstPayload : number, telegram : number[]) {
-            this._startCharacter = startCharacter
-            this._frameLength = frameLength
-            this._firstPayload = firstPayload
+            this.__startCharacter = startCharacter
+            this.__frameLength = frameLength
+            this.__firstPayload = firstPayload
             this._telegram = telegram
-            this._payloadLength = this._frameLength - 6
+            this.__payloadLength = this.__frameLength - 6
 
         }
 
 
         toJSON() : any {
-            return MeterbusLibUtils.jsonPrepaper(this, ["_startCharacter", "_frameLength", 
-               "_firstPayload", "_payloadLength" ])
+            return MeterbusLibUtils.jsonPrepaper(this, [])
         }
 
         getJSON() : string {
@@ -30,12 +29,12 @@ export namespace MeterbusLibFrames {
         }
 
         verifyChecksumAndEnd() {
-            if (this._firstPayload != 0) {
+            if (this.__firstPayload != 0) {
                 if (this._telegram[this._telegram.length - 1] != 0x16) {
                     throw new MeterbusLibExceptions.InvalidStopCharError()
                 }
                 let checksum : number = 0
-                this._telegram.slice(this._firstPayload, this._telegram.length -2).forEach((val) => {
+                this._telegram.slice(this.__firstPayload, this._telegram.length -2).forEach((val) => {
                     checksum += val
                 })
                 // console.log(`calc. checksum ${checksum}, ${checksum & 0xff}`)
@@ -49,10 +48,10 @@ export namespace MeterbusLibFrames {
         abstract parse2()
 
         parse() {
-            if (this._telegram[0] != this._startCharacter) {
+            if (this._telegram[0] != this.__startCharacter) {
                 throw new MeterbusLibExceptions.InvalidStartCharError()
             }
-            if (this._telegram.length != this._frameLength) {
+            if (this._telegram.length != this.__frameLength) {
                 throw new MeterbusLibExceptions.InvalidLengthError()
             }
             this.verifyChecksumAndEnd()
@@ -83,10 +82,10 @@ export namespace MeterbusLibFrames {
         }
 
         parse2() {
-            if (this._telegram[2] != this._payloadLength) {
+            if (this._telegram[2] != this.__payloadLength) {
                 throw new MeterbusLibExceptions.InvalidSecondLengthError()
             }
-            if (this._payloadLength < 3) {
+            if (this.__payloadLength < 3) {
                 throw new MeterbusLibExceptions.PayloadTooShortError()
             }
 
diff --git a/src/utils.ts b/src/utils.ts
index ad3b3b2..3f42a9a 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -17,10 +17,7 @@ export namespace MeterbusLibUtils {
     export function jsonPrepaper(obj:any, hideKeys:string[]) : any {
         let dup = {}
         for (let key in obj) {
-            if (hideKeys.indexOf(key) == -1) {
-                //if (key[0] == "_") {
-                //    key = key.slice(1)
-                //}
+            if ((hideKeys.indexOf(key) == -1) && ! ((key[0] == "_") && (key[1] == "_"))) {
                 let dkey = (key[0] == "_") ? key.slice(1) : key
                 dup[dkey] = obj[key]
             }