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42004-438A
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MERGENCY
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ELEPHONE
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ANUAL
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f:\standard ioms - current release\42004 instr. manuals\42004-438a.doc
02/11
Early Microphone Option
The microphone in each telephone activates only after the unit determines connection to the called party.
Based on factory-default programming, this will occur in one of two ways; when the telephone receives a
DTMF “*” from the called party or when the telephone detects that no more ring-backs from the called
number are occurring. This ring-back determination may take 4–6 seconds to detect, rendering the
microphone non-active for that time.
Enabling Early Microphone activates the microphone when the telephone begins checking for ring-back
tones, typically within less than 1 second after the unit completes the dialing sequence. If enabled, Early
Microphone operation will occur for both emergency and non-emergency call operation of the Model
398-001 and 394AL-001 Telephones.
Use of the Early Microphone feature includes an operational risk that ring-back tones can be missed or
audio received by the microphone can be recognized by the telephone, causing it to operate as if the call
had been answered. This could prevent call “rollover” from occurring.
It is strongly recommended that the Early Microphone feature be used only if the telephone number being
called by the emergency telephone is attended 24 hours per day. If call rollover is desired, the use of the
DTMF “*” for microphone activation is strongly recommended (default).
Feature
Key
Sequence
Description
Default
Early
Microphone
Option Enable
# 7 1 1
Provide microphone activation within 1 second of dial
sequence completion.
No
Early
Microphone
Option Disable
# 7 1 0
Returns telephone to default operation of microphone.
Yes
