SA541

sames

12/16

DTMF Mode Timing Diagram

10. 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 4: DTMF Mode Timing Diagram