They are interesting for the fact that they are very plain and undecorated for the time, with only one plain central panel at the back and no armrests.
很有趣的是，当时它们很普通，没有装饰，只是后面有一个简单的中央面板，没有扶手。
2
Prior to assembly, grooves were made in the shelf, base, and sides to accommodate the backpanel.
在组装之前，隔板、底座和侧面已开槽以便与背板相嵌。
《柯林斯英汉双解大词典》
3
To get started, assign all mics and instruments to their channels by connecting them to the corresponding jacks on the backpanel.