Update:- 12/04/2023 

Consider a terminal connected to the Network at the Network Termination Point , NTP.

[terminal]---+---[ line ]---[exchange]
            NTP
			
What is the Zc of the Terminal?
What is the Zc of the Exchange?
What is the Z looking into the line towards the Exchange at the NTP?
What is the Z looking into the line towards the Terminal at the Exchange?

The NTP is nominally 2km from the Exchange.

Artificial Line - calculate Zterm to give zero side tone for different line lengths. Not sure if this is useful.

SIN 351 gives two complex impedances.
Complex Z add exchange Z = 370+ 620//310nf [ :
//The terminal Figure 1: Terminal Complex Impedance Network = 370+ 620//310nf
//The nominal exchange input impedance is 300 ohm + 1000 ohm || 220 nF (see Figure 2). //12/04/2023 - nominal exchange input impedance at the NTP should include 2km line Use Shunt Termination when you need Io =0 and Vo != 0

Use Series Termination when you need Vo =0 and Io != 0


we need to plot what we present. we want V/I 

--[line]--[hybrid]===
V near Voltage,I near Current
v far voltage, i far current

NOTE: Iin, i  flows into the two port Two Port network, Iout or I flows out.  This enables the line to be chained together.

[V]  = [ ][M]
[I]       [E]

If E=0 then V/I is Zbalance to give E=0

V/I = A/B for E=0

For different line lengths calculate V/I = Z required to give zero side tone.

use converrt to get:

[V]  = [ ][M]
[I]       [E]

[I]  = [ ][V]
[E]       [M]

[E] = [ ] [I]
[M]       [V]

[M] = [ ] [E]  
[V]       [I]


when E=0 D = V/I=Z
also work out V = 0.1 |E|+ D I
mag:
all:
Calculation [ A B C D ]: C = Iin/Vout converted to V/i
Edit the source code to enter the phone and exchange data.