diff --git a/extras/doc/Quectel_M95_GSM_Specification_V3.1.pdf b/extras/doc/Quectel_M95_GSM_Specification_V3.1.pdf
deleted file mode 100644
index b73c228..0000000
Binary files a/extras/doc/Quectel_M95_GSM_Specification_V3.1.pdf and /dev/null differ
diff --git a/src/TinyGsmClientBG96.h b/src/TinyGsmClientBG96.h
index ac76365..b1d6d49 100644
--- a/src/TinyGsmClientBG96.h
+++ b/src/TinyGsmClientBG96.h
@@ -308,8 +308,9 @@ public:
   }
 
   bool poweroff() {
-    sendAT(GF("+QPOWD"));
-    return waitResponse(GF("POWERED DOWN")) == 1; // TODO
+    sendAT(GF("+QPOWD=1"));
+    waitResponse(300);  // returns OK first
+    return waitResponse(300, GF("POWERED DOWN")) == 1;
   }
 
   bool radioOff() {
diff --git a/src/TinyGsmClientESP8266.h b/src/TinyGsmClientESP8266.h
index b6da2b2..b43ca12 100644
--- a/src/TinyGsmClientESP8266.h
+++ b/src/TinyGsmClientESP8266.h
@@ -297,7 +297,10 @@ public:
     return init();
   }
 
-  bool poweroff() TINY_GSM_ATTR_NOT_IMPLEMENTED;
+  bool poweroff() {
+    sendAT(GF("+GSLP=0"));  // Power down indefinitely - until manually reset!
+    return waitResponse() == 1;
+  }
 
   bool radioOff() TINY_GSM_ATTR_NOT_IMPLEMENTED;
 
diff --git a/src/TinyGsmClientM95.h b/src/TinyGsmClientM95.h
index 6b01da1..88f99b7 100644
--- a/src/TinyGsmClientM95.h
+++ b/src/TinyGsmClientM95.h
@@ -316,8 +316,8 @@ public:
   }
 
   bool poweroff() {
-    sendAT(GF("+QPOWD"));
-    return waitResponse(GF("POWERED DOWN")) == 1; // TODO
+    sendAT(GF("+QPOWD=1"));
+    return waitResponse(300, GF("NORMAL POWER DOWN")) == 1;
   }
 
   bool radioOff() {
diff --git a/src/TinyGsmClientUBLOX.h b/src/TinyGsmClientUBLOX.h
index e34504e..0fb513c 100644
--- a/src/TinyGsmClientUBLOX.h
+++ b/src/TinyGsmClientUBLOX.h
@@ -325,7 +325,10 @@ public:
     return init();
   }
 
-  bool poweroff() TINY_GSM_ATTR_NOT_IMPLEMENTED;
+  bool poweroff() {
+    sendAT(GF("+CPWROFF"));
+    return waitResponse(40000L) == 1;
+  }
 
   bool radioOff() {
     sendAT(GF("+CFUN=0"));
diff --git a/src/TinyGsmClientXBee.h b/src/TinyGsmClientXBee.h
index 0c82962..d969d93 100644
--- a/src/TinyGsmClientXBee.h
+++ b/src/TinyGsmClientXBee.h
@@ -402,7 +402,9 @@ public:
     exitCommand();
   }
 
-  bool poweroff() TINY_GSM_ATTR_NOT_IMPLEMENTED;
+  bool poweroff() {  // Not supported
+    return false;
+  }
 
   bool radioOff() TINY_GSM_ATTR_NOT_IMPLEMENTED;
 
diff --git a/src/TinyGsmCommon.h b/src/TinyGsmCommon.h
index 2cd7827..f1d5729 100644
--- a/src/TinyGsmCommon.h
+++ b/src/TinyGsmCommon.h
@@ -239,6 +239,7 @@ public:
    */
 
   virtual bool restart() = 0;
+  virtual bool poweroff() = 0;
 
   /*
    * SIM card functions - only apply to cellular modems
@@ -282,6 +283,7 @@ public:
     return false;
   }
   virtual bool gprsDisconnect() { return false; }
+  virtual bool isGprsConnected() { return false; }
 
   /*
    * IP Address functions