Labels:text | screenshot OCR: INBAND INTEGRATION TOPOLOGY Analog Analogy Trunk Central ports on ports on ports on' ¿office PBX PBX switch Analog telephones, Figure 1. Inband integration requires that you already have a PBX. Trunk ports on the PBX connect to the central office. Analog ports on the PBX connect to the Voice Response Unit { VRU) and to analog telephones.