3.1 GUIDELINES FOR INTEGRATIONINTEGRATING THE VPS WITH PANASONIC KX-T PHONE SYSTEMS 43The VPS must also have access to certain PBX features. For example, if the VPS takes amessage, one way it can notify the mailbox owner is by dialing the PBX's Message-Waiting-Lamp-On code. Once new messages are retrieved, the VPS dials the Message-Waiting-Lamp-Off code for that same mailbox owner.3.1.4 PBX Requirements for IntegrationThe PBX must have certain capabilities and features to work with the VPS. (Although thissection includes tests to help you evaluate the PBX, it may be necessary to refer to the PBX'sdocumentation for detailed capability and feature descriptions.)Single Line (Tip/Ring) Port CircuitsThe VPS can only be connected to a PBX that supports SLT sets. Some PBXs need an OPXcard to provide this connection. However, some OPX cards do not provide all the capabilitieslisted in this section.Following are the minimum current and voltages that the PBX must supply:Station to Station DTMF SignalingFor system users to access VPS services and features, they must be able to send DTMF tonesfrom their telephones to the VPS port. As a general rule, SLT sets can perform station-to-station DTMF signaling; however, many proprietary telephones cannot. Some PBXs need tobe programmed to make proprietary sets use DTMF signaling.If the PBX does not provide station-to-station DTMF signaling, VPS services and featureswill be limited.DTMF TonesTable 9Minimum Loop Current 20 mAMinimum Line Voltage 7 V DCMinimum Ringing Voltage 40 V ACTEST:Call an SLT extension from the telephone in question. When the callis answered, see if the person receiving the call hears DTMF tones whennumbers are dialed.Table 8VPS/PBX COMMUNICATION
