Recommendation U.25

REQUIREMENTS FOR TELEX AND GENTEX OPERATION

TO BE MET BY CODE- AND SPEED-DEPENDENT TDM SYSTEMS

CONFORMING TO RECOMMENDATION R.101

(Geneva, 1980)

The CCITT,

considering

(a)	that it may be desirable to use code- and speed-dependent TDM systems described in Recommendation R.101 in the teleprinter switching networks;

(b)	that it is essential to transmit the full range of telex signals for types A, B, C and D signalling;

unanimously declares

that the following requirements for telex and gentex operation should be met by code- and speed-dependent time division multiplex systems conforming to Recommendation R.101.

1	Transmission of type A (control) signals shall be accomplished within the tolerances specified in Table 1/U.25.

2	Transmission of type B (control) signals shall be accomplished within the tolerances specified in Table 2/U.25.

3	Transmission of type C signals shall be accomplished in accordance with Table 3/U.25.

4	Transmission of type D signals shall be accomplished in accordance with Recommendation U.12.

5	Each of the following modes of bothway telex signalling shall be capable of being accomplished on a single circuit:

a)	type A in one direction and type B keyboard in the other;

b)	type A in one direction and type B dial in the other;

c)	type B keyboard in one direction and type B dial in the other;

d)	type A in both directions;

e)	type B dial in both directions;

f)	type B keyboard in both directions;

g)	type C to Table 1/U.11;

h)	type C to Table 2/U.11;

i)	type C to Table 3/U.11.

6	A single terminal shall be capable of handling any of the signalling combinations shown in S 5 above and at least five of them simultaneously.

7	The nominal pulse duration (other than dial pulses) shown in Tables 1/U.25, 2/U.25 and 3/U.25 for Signal transmitted to telex have a 3 ms tolerance except where otherwise indicated.

TABLE 1/U.25

Montage: Reprendre les originaux du Livre Rouge (sans corr.)

TABLE 2/U.24

Montage: Reprendre les originaux du Livre Rouge (sans corr.)

TABLE 3/U.25

Montage: Reprendre les originaux du Livre Rouge (sans corr.)