Question: what are the types of telephone communication?
Answer: 3.1 PSTN Line (Analogue)
3.2 Common Issues with PSTN (Analogue) Telephone Lines.
3.3 Multiline.
3.4 Digital Lines.
3.5 ISDN2.
3.6 ISDN30.
3.7 Advantages and Disadvantages of ISDN.
3.8 SIP - Session Initiation Protocol Trunking.