Cisco Spark hybrid call service integrates Cisco Spark with an existing Cisco call-control platform, such as Cisco Unified Communications Manager, Cisco Business Edition 6000/7000, or Cisco Hosted Collaboration Solution. This integration enables users to make and receive calls on their Cisco device or Spark application using the same dialing procedure as with on-premises registered endpoints. For example, users can dial extension numbers, PSTN numbers, or URIs from their Cisco device or Spark application and reach any destination that is reachable from their on-premises call-control platform.

Cisco Spark hybrid call service has two service components, called Call Service Aware and Call Service Connect1. Call Service Aware makes Cisco Spark aware of calls within your existing Cisco call control. It enables features such as call history, missed call notifications, and one-button-to-push join for meetings on Cisco Spark. Call Service Connect enables calls between Cisco Spark and your existing call control so that, to users they appear as one system. It allows users to make and receive calls on their Cisco device or Spark application using their enterprise directory number, regardless of their location or network. It also enables features such as single number reach, shared line appearance, and call transfer and forwarding.

Therefore, the correct answer is Call Service Connect, as it is the Cisco Spark hybrid call service component that integrates Cisco Spark with an existing Cisco call-control platform and makes it possible for users to make and receive calls on their Cisco device or Spark application using the same dialing procedure as with on-premises registered endpoints.

References := Cisco Spark Hybrid Services Data Sheet, The best of both worlds – Cisco Spark Hybrid Services