beat drums and clang gongs -- in + battle

'Beating drums and ringing gold' is a way of commanding and transmitting information on ancient battlefields in China. When drumming, advance; when ringing gold, retreat.

The unit is designed for unsupervised public use: controls are recessed or shielded, moving parts are enclosed, and the interface is operable by a child of about six with no instruction. Where a screen is used, the language can be switched without changing the hardware, and the content can be replaced on site.

Entering at the sound of drums and retreating at the sound of gold "is a common sense in ancient military. On battlefields with as few as thousands, as many as tens or even hundreds of thousands of people, the commander's voice cannot be heard by the entire army, so messages can only be conveyed through the sounds of drums and gold. In ancient times, war drums were used in the military not only for commanding troops and transmitting messages, but also for inspiring morale and intimidating the enemy. Zheng is an ancient musical instrument that resembles a bell and is narrow and long, with a handle that produces sound when struck. It is made of copper. The sound produced by the copper cast Zheng is crisp and loud, with a deep and distant aftertaste. When two armies are engaged in battle, people shout and horses neigh, and the sound of fighting is constant. At this time, a particularly loud object is needed to convey orders, and the sound of the spear is clear and loud, with strong penetrating power. Even in intense fighting, soldiers can hear it.