USB host function allows you to connect to various peripherals on the device by USB interface. Unfortunately, USB host is quite rare in HTC products.
Interestingly, the company’s specialists have recently developed and patented a universal USB host adapter. In addition to its immediate task of connecting devices, the adapter provides power to devices connected by USB interface.
The smartphone HTC HD2, as we know, has USB host function, but it is only active when you connect an external power source. Therefore, according to some web resources, production of such enhancement was expected.