Terminology

 https://en.wikipedia.org/wiki/Echo_suppression_and_cancellation

https://wiki.analog.com/resources/tools-software/sigmastudio/toolbox/adialgorithms

Telecordia Standards like  GR-283-CORE

pulse timer - https://www.wisdomjobs.com/e-university/programmable-logic-controllers-tutorial-523/pulse-timers-14725.html#:~:text=Pulse%20timers%20are%20used%20to,output%20from%20some%20initiating%20input.&text=When%20there%20is%20an%20input%20to%20In%201%2C%20there%20is,elapsed%2Cthe%20timer%20contacts%20open.

line feeding - feeding of line changes from standby to active to different state depends on on-hook off-hook , and other line status

howler tone -

howler mode -  

ring cadence - 

polarity reversal - Polarity of the line will be reversed, +- of a/b wire of RJ11
polarity means dc voltage, it is the directional flow of electrons from one pole to the other

https://www.ixysic.com/home/pdfs.nsf/www/an-118.pdf/$file/an-118.pdf

special information tone -

call waiting tone -

loopback circuit -loopback, or a loop, is a hardware or software method which feeds a received signal or data back to the sender. It is used as an aid in debugging physical connection problems.

subscriber loop -

Testing - (read G.996.2 document T-REC-G.996.2-200905-S!!PDF-E%20.pdf)

http://www.dsltesting.eu/36/Selt-Delt-Melt.htm

https://patents.google.com/patent/WO2006039419A1

MLT (Metallic Line testing)

TR-286 Testing of Metallic Line Testing (MELT) functionality on xdsl Ports

https://patents.google.com/patent/EP1193958A1/ar

PBLT(Physical Line test)

Silence suppression - The term silence suppression is used in telephony to describe the process of not transmitting information over the network when one of the parties involved in a telephone call is not speaking, thereby reducing bandwidth usage