Ccittr2

This method is commonly used on one-way trunks, is tone-on-idle, and provides two-state signaling. The forward and backward signals and transition states are similar to Bell System MF signaling and are illustrated in Table 3-7.

Table 3-7. CCITT-R2 Supervision Signals

Direction

Signal Type

Transition

Forward

Seizure

Tone-on to tone-off

Forward

Clear-forward

Tone-off to tone-on

Backward

Answer

Tone-on to tone-off

Backward

Clear-back

Tone-off to tone-on

Backward

Release-guard

Tone-off to tone-on

Backward

Blocking

Tone-on to tone-off

National R2

National R2

National R2 signaling has many country variants. Most versions of National R2 use pulse out-of-band supervision signals, however. Examples of National R2 supervision signals are illustrated in Table 3-8.

Table 3-8. Examples of National R2 Supervision Signals

Direction

Signal Type

Pulse Duration in ms

Forward

Seizure

150

Forward

Clear-forward

600

Backward

Answer

150

Backward

Clear-back

600

Backward

Release-guard

600

Backward

Blocking

Continuous

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