Detecting phone line various states

[taskmn57]

Hi All,
I am designing a circuit which want to
record phone line conversations using microcontroller
I need to detect line busy, free line,on hook or
off hook line status.
Is there any circuit or information for
these line states?
Is there any software algorithms
which I can use in my microcontroller firmware
for this purpose?
I would appreciate any help?
Thanks in advance,
Hossein

 

[kak111]

Here is some reading for you...................to get starting ....

Telephone interfacing circuits

Signals and Circuit Conditions

Special information tones - Wikipedia, the free encyclopedia

**broken link removed**

https://www.electro-tech-online.com/attachments/microcontrollers/8782d1153404482-download-free-articel-about-telephon-line-introduction-telephone-line-interfacing-using-pic-microcontroller.pdf

Elektronika.ba - Phone recorder

Regards KAK