Tesis previa a la obtención del Título de Ingeniero en Electrónica y ...

- data transmission within a multilayer protocol, either in the I-channel (MLP) or in capacity other than the Ichannel
(H-MLP);
- an encryption control signal;
- loopback towards the network for maintenance purposes;
— signalling for control and indícations;
- a message system for, Ínter alia, conveying information concerning equipment manufacturer and lype.
,e command BAS attributes have the following signifícance: on receipt of a BAS command code in one (even) frame
d its error-correcting code ín the next (odd), the receiver prepares to accept the stated mode change beginning from the
bsequent (even) frame; thus a mode change can be effected in 20 milliseconds. The command remains in forcé until
untermanded (see 12/H.242), The bit positions occupied by combinations of BAS commands are exemplified in Figures
to 5g.
e capability BAS attributes have the following signifícance: they indícate the ability of a terminal to receíve and
)perly treat the various types of signal. It follows that having received a set of capability valúes from the remote terminal
terminal X must not transmít signáis lying outside that declared range.
ilues [0-7] ofthe attribute (111) are reserved for setting the class, and [8-15] for setting the family; the default valué is
30) for both,
ie next eight attribute valúes ofthe attribute (111) are temporary escape BAS codes of single byte extensión (SBE). The
¡t three bits ofthe temporary escape BAS form a pointer to one of eight possible escape BAS tables of 224 entries each
)des beginning wíth 111 are not used in the escape BAS tables). Then the next received BAS indícales the specific
try Ín the escape BAS table.
e valué (111) [24] is the capability marker (see 2/H.242) which is followed by normal BAS codes, not by any escape
lúes.
e last seven attribute valúes ofthe attribute (111) are of múltiple byte extensión (MBE) and are used lo send messages
specified in the Notes to Tables A.2 and A.3.
Bit number
7 8
1
2
8
9
16
17
19
143
:
:
FAS
BAS
18
20
144
FIGURE 5a/H.221
Oclal
number
Bit numbering and positíon for 14.4 kbit/s LSD
16
17
18
80
Recommendation H.221 (03/93) 11