[doc] Extend FAQ (sandeepmistry#96)

* [doc] Extend FAQ

* Update README.md

Author: Rotzbua

README.md

@@ -2,7 +2,7 @@
 
 [![Build Status](https://travis-ci.org/sandeepmistry/arduino-LoRa.svg?branch=master)](https://travis-ci.org/sandeepmistry/arduino-LoRa)
 
-An [Arduino](http://arduino.cc/) library for sending and receiving data using [LoRa](https://www.lora-alliance.org/) radios.
+An [Arduino](https://arduino.cc/) library for sending and receiving data using [LoRa](https://www.lora-alliance.org/) radios.
 
 ## Compatible Hardware
 
@@ -73,8 +73,16 @@ No, all data is sent unencrypted. If want your packet data to be encrypted, you
 
 This library exposes the LoRa radio directly, and allows you to send data to any radios in range with same radio parameters. All data is broadcasted and there is no addressing. LoRaWAN builds on top of LoRA, but adds addressing, encryption, and additional layers. It also requires a LoRaWAN gateway and LoRaWAN network and application server.
 
+**5) Does this library honor duty cycles?**
 
+No, you have to manage it by your self.
+
+**6) Which frequencies can I use?**
+
+You can use [this table](https://www.thethingsnetwork.org/wiki/LoRaWAN/Frequencies/By-Country) to lookup the available frequencies by your country. The selectable frequency also depends on your hardware. You can lookup the data sheet or ask your supplier.
+
+Please also notice the frequency dependent duty cycles for legal reasons!
 
 ## License
 
-This libary is [licensed](LICENSE) under the [MIT Licence](http://en.wikipedia.org/wiki/MIT_License).
+This libary is [licensed](LICENSE) under the [MIT Licence](https://en.wikipedia.org/wiki/MIT_License).