Call forwarding is a service that automatically redirects incoming calls to another phone number. NTT East/West's Voice Warp and mobile carrier forwarding services are representative examples. Since you can receive office or home calls while away, it is widely used as a means of preventing missed business opportunities.
There are three main forwarding modes. Unconditional forwarding immediately redirects all calls to the forwarding destination. No-answer forwarding redirects after a set number of rings (typically 5-6) without answer. Busy forwarding redirects calls received while already on a call. Combining these enables flexible call handling based on the situation.
An important cost consideration: call charges from the forwarding source to the forwarding destination are borne by the forwarding source's subscriber. For example, when forwarding from a Tokyo office (03) to an Osaka mobile phone, the caller only pays local call rates, but the forwarding source subscriber incurs Tokyo-to-Osaka call charges. Forwarding to mobile phones costs more than to landlines, so pre-estimating monthly costs is important.
Recently, more companies are using cloud PBX to achieve more flexible call routing than traditional forwarding. Settings can automatically switch forwarding destinations by time of day or day of week, or ring multiple devices simultaneously. For personal use, mobile forwarding settings can route calls to voicemail during work hours and to a home landline after work. Note that call charges apply to the forwarding destination number. Forwarding to mobile phones is particularly expensive, so costs can be reduced by forwarding to landlines or IP phones instead. Review forwarding usage in the business phone number guide.