3.1 GUIDELINES FOR INTEGRATIONInstallation Manual 45The 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 thecapabilities listed in this section.Following are the minimum current and voltages that the PBX must supply:Station to Station Touchtone SignalingFor system users to access VPS services and features, they must be able to send touchtonesfrom their telephones to the VPS port. As a general rule, SLT sets can perform station-to-station touchtone signaling; however, many proprietary telephones cannot. Some PBXs needto be programmed to make proprietary sets use touchtone signaling.If the PBX does not provide station-to-station touchtone signaling, VPS services andfeatures will be limited.Table 3-1 VPS/PBX COMMUNICATIONPBX to VPS VPS to PBXCall Progress Tones• ringback• busy• reorderTouchtonesSLT Signals• on/off hook• hookswitch flash• touchtonesTable 3-2Minimum 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 touchtones whennumbers are dialed.
