The hybrid circuit summarized
nThe
hybrid circuit transforms two-wire connection into 4-wire
connection.
nIf
the hybrid is unbalanced echo will result
nHybrid is balanced when no own voice is leaked into own
loudspeaker
nHybrid
unbalance can result from line impedance changes due to weather
conditions
nUnbalance
results echo
nEcho
cancellation circuits are harmful in data connections
nNowadays
realized by operational amplifier based circuitry that
automatically monitors line impedance changes