sames

SA545

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11. Loop Disconnect Dialling (Figures 5 and 6)

The MASK output is provided in order to disable the speech circuit during LD dialling.

Consequently, the MASK output is normally at logic '1' in the off-hook condition, but

changes to logic '0' during LD dialling. MASK also changes to logic '0' in order to

signal a Timed Break Recall (Flash) to the line. Both MUTE and MF OUT remain

low during LD dialling.

LD dialling is signalled on the IMP output. A break is signalled by a logic '0', make

periods and IDP times are signalled by a logic '1'. When not dialling, the IMP output

remains at logic '0'.

Figure 5: LD Mode Timing Diagram

Figure 6: Detailed Timing for IMP Output

t

1

= Pre-digit Pause (= t

t

2

= Break Period (60ms or 67ms)

t

3

= Make Period (40ms or 33ms)

t

4

= Post-digit Make (= t

3

)

t

5

= Inter-digit Pause (800ms or 500ms)