Instruction manual

ACU-1000 Operations Manual
2-102 Interoperability Now
2.17.3.5 DTMF Mute Timer
When a module is not in the Data Mode (See Section 3.5.1.9), all DTMF signals detected in the
receive audio are interpreted as commands meant for the receiving module. When the DTMF
Mute Timer is enabled, these DTMF command signals are “Muted”; that is, they are not passed
on to the ACU-1000 internal audio bus to be routed to another module, nor are they sent back
out in any module’s TX audio. A module cannot instantaneously mute a DTMF signal; some
time is required to detect its presence. Therefore, when a DTMF signal first becomes present in
the receive audio, a short burst is passed through. The DTMF mute timer ensures, if a long
string of DTMF characters are present in the receive input, a short burst of only the first DTMF
character is passed through. This is accomplished by muting the audio as soon as the first
character is detected, and then keeping the audio muted until the first character is complete, and
until enough of the next character has been received so it is detected while the audio is still
being muted. Each time a new DTMF character is detected, the timer is reset. When the timer
expires (because no new DTMF character is detected in the receive input), the audio is no
longer muted.
The factory default is DTMF Mute Timer Disabled, as the majority of ACU-1000 systems do
not employ DTMF control. This setting allows the DTMF signals to be passed through the
system like all other audio. It also prevents inevitable occasional “falsing” on voice signals that
are similar to a DTMF character; this falsing would momentarily mute throughput audio.
If DTMF control is used, it may be desirable to mute the DTMF characters as they may be
annoying to other system users, and a timer setting 1 second works well in most cases. If the
setting is too low (because some system users transmit DTMF characters slowly), a short burst
of DTMF will be passed through at the start of each DTMF character. The timer should be set
to a value that is longer than the maximum time elapsed between the end of one DTMF
character and the start of the next.
There are some circumstances when it’s important that incoming DTMF not be interpreted by
the ACU-1000 as control input, but instead must be passed to other equipment. The settings
used are different depending on whether the module that’s passing on the DTMF is a PSTN
module (which regenerates DTMF) or any other type of module (which do not).
The factory default for the PSTN-2 disables the mute delay timer.
2.17.3.6 RX Audio Delay
An adjustable delay can be added to the PSTN-2’s input audio. When speech first appears in
the input audio, some time passes before it can be detected by the VOX algorithm. The
adjustable audio delay prevents the loss of the audio that is received before the detection takes
place and audio gates can be opened to send this audio on to other modules.
The factory default is 35 ms.