TD-H Series Series The TD-H Series is a multi-channel selective-call handset intercom system. With five different sized handsets, the system can be configured to meet most selective calling application. Freakishly Reliable Aiphone is proud to be a rare, two-time winner of the prestigious Deming Prize for quality management and manufacturing processes. Our ISO Certified process and rigorous standards result in some of the most reliable products in the industry. Aiphone products routinely last for years, only being replaced when the application outgrows the system capacity.