1 General
2
Characteristics of interfaces
2.1 Characteristics of interface C2
2.1.1 Exchange impedance
2.1.2 Impedance unbalance about earth
2.1.3 Relative levels
2.2 Characteristics of interface Z
2.2.1 Exchange impedance
2.2.2 Impedance unbalance about earth
2.2.3 Relative levels
3
Characteristics of half-connections
3.1 Characteristics common to all 2-wire analogue interfaces
3.1.1 Transmission loss
3.1.2 Group delay
3.1.3 Single frequency noise
3.1.4 Crosstalk
3.1.5 Total distortion including quantizing
distortion
3.1.6 Discrimination against out-of-band
signals applied to the input interface
3.1.7 Spurious out-of-band signals received at
the output interface
3.1.8 Echo
and stability
3.2 Characteristics of interface C2
3.2.1 Nominal value of transmission loss
3.2.2 Noise
3.2.3 Values of total distortion
3.3 Characteristics of
interface Z
3.3.1 Nominal value of transmission loss
3.3.2 Noise
3.3.3 Values of total distortion
Appendix I – Impedance strategy in 2-wire networks
I.1 Introduction
I.2 General equations for unloaded cables
I.3 General impedance considerations of a hybrid
I.3.1 Cable input impedance Z2 and
the hybrid input impedance ZT
I.3.2 Balance impedance ZB
I.4 Echo considerations
I.4.1 Talker echo loudness rating TELR
I.4.2 Sidetone masking rating STMR and listener
sidetone rating LSTR
I.5 Applications
I.6 Analysis of loop impedance variation by means of a special
impedance diagram
I.7 Conclusions
I.8 Examples of impedances Z2 and compromise nominal
impedances ZT and ZB
I.8.1 Cable input impedance Z2 and
hybrid input impedance ZT
I.8.2
Balance impedance ZB
I.8.3 Application of the special impedance
diagram
I.8.4 Echo considerations
References