Question 22/XII - International telephone conference
(continuation of Question 32/XII studied in 1984- 1988)

Recommendations E.151 and G.172 contain relevant information with
respect to the network arrangements and equipment used to establish
voice telephone conferences. Considering these existing Recommendations.

What should be recommended in respect of transmission performance to
enable international telephone conference calls to be satisfactorily
accomplished?

In particular,

a) What transmission characteristics should be recommended in respect to
the bridging equipment to be used?

b) What transmission restrictions should be recommended for the other
facilities used in connections for international conference calls?

c) What considerations should be given with respect to the transmission
of non-speech signals (e.g. voice band data, facsimile, graphics, slow
scan television, etc.) on international telephone conference
connections?

Note 1 - Characteristics of interest for the bridging equipment include:

- insertion loss;

- automatic gain control;

- features for control of stability and echo;

- features for control of noise accumulation;

- special requirements for sending non-speech signals.

Note 2 - In Part B, consideration should be given to:

-application rules for using switched gain (loss) devices (e.g., loud-
speaking telephones, echo suppressors, bridging equipment, etc.) in
tandem;

-the relationship between the transmission performance of customer
premises and bridging equipment;

-the use of satellite circuits;

-the consequences of multiple star conference connections, especially
those employing more than a single satellite circuit.