Call transfer automatically forwards incoming calls to a preset number. Services include NTT's "Voice Warp" (550 yen/month), Docomo's "Call Forwarding" (free), and au's "Call Transfer" (free).
Three main types exist: "unconditional" (all calls forwarded immediately), "no-answer" (forwarded after set rings without pickup), and "busy" (forwarded when line is occupied). Combinations enable flexible call handling.
Business uses include forwarding to traveling sales staff, after-hours answering services, and telework employees' mobiles. Combined with PBX extension transfers, it ensures customers reach the right person.
Note that forwarding call charges are borne by the forwarder's account. Heavy mobile forwarding can be expensive. Forgetting to disable forwarding risks calls going to unintended numbers. See business phone guide for details.