MWI = Message Waiting Indicator

Usually an audio or visual signal that a voicemail or other type of message is waiting. Examples:

• Stutter dial-tone
• Flashing light on phone
• Vibration
• Periodic special ring
• etc.

IP phones

Most IP phones support a MWI indicator, and most ATA's support stutter dial-tone. Asterisk also supports stutter tone on Zaptel FXS adapters.

The following ATAs can be configured to additionally light an LED on the base unit for MWI:

• Grandstream HT488
• Sipura SPA-3000
• Linksys PAP-2
• AudioCodes MediaPack FXS Gateways

The following IP phones are known have trouble displaying MWI:

• Budgetone BT-101/BT-102 claims to, but does not (Wrong: The LCD backlights blicks to indicate MWI)

Analog phones

Some analog phones also support MWI via a 90V neon lamp - requires hardware support on the FXS interface. Supported by:

• Xorcom Astribank
• AudioCodes MediaPack FXS Gateways (applies 100V DC on line for bulb in handset)

ISDN phones/devices

Have a look at ETS 300 650 and ETS 300 196 (www.etsi.org). To do this stuff with a PC and a standard ISDN controller have a look at
CAPI 2.0 4. edition part 3 "Supplementary Services" (www.capi.org)
It would come in an "Information" message with a Feature Activation for the proper button/key number.

See also:

• SIP MWI
• Asterisk MWI
• Asterisk SIP Mailbox
• Mobile MWI
• Asterisk config zapata.conf mailbox keyword.

Not to be confused with: MBWA