Panasonic KX-TVM50 installation manual Dtmf Signalling, Message Waiting Notification on an SLT

5.1 Guidelines for Inband Integration

Following are the minimum current and voltages that the PBX must supply:

Minimum Loop Current	20 mA
Minimum Line Voltage	7 V DC
Minimum Ringing Voltage	40 V AC

DTMF Signalling

For system users to access VPS services and features, they must be able to send DTMF signals from their telephones to the VPS port. As a general rule, most SLTs can send DTMF signals; however, many proprietary telephones cannot. Some PBXs need to be programmed to make proprietary telephones use DTMF signalling.

TEST: Call an SLT extension from the telephone in question. When the call is answered, see if the person receiving the call hears DTMF tones when numbers are dialled.

Message Waiting Notification on an SLT

When the Message-Waiting-Lamp-On code is dialled by the VPS, either the lamp on the corresponding extension should light or the extension should receive a stutter dial tone. The VPS functions best when the extension number of the mailbox subscriber follows the Light-On or Light-Off code. On some PBXs, however, the extension number is dialled first, followed by a hookswitch flash and then the On code. This presents a problem if the extension is answered before the VPS sends the hook-switch flash.

If the PBX does not provide Message Waiting Notification on an SLT, the VPS can only notify mailbox owners by dialling a beeper number or user-assigned extension.

This process slows down VPS performance as it dials the beeper or extension number and waits to confirm notification. The beeper or user-assigned extension notification is meant to be used for necessity, usually for mailbox owners who are often out of the office (e.g., sales people or field representatives). The only other option, without Message Waiting Notification is for mailbox owners to periodically call the VPS to check for messages.

TEST: See if dialling the On code from an SLT can turn on an extension's message waiting indicator.

Screened Transfer from an SLT

The PBX must provide a screened transfer from an SLT for the VPS to function properly.

A screened transfer:

1.Puts the caller on hold, usually with a hookswitch flash.

2.Dials the extension.

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