This manual covers the installation and wiring of the HT-990 telephone, including safety precautions and step‑by‑step connection instructions. It also explains how to adjust volume levels and other basic operating functions.
A troubleshooting section helps identify common faults and provides guidance on when to contact service support. The document includes diagrams and notes to assist users in proper use and maintenance of the telephone. This manual is written in Japanese.
Use the volume adjustment switch, selecting large, medium, or small as needed.
Refer to the troubleshooting section and follow the listed steps, or contact the service center for assistance.