Figure 1 shows the JCS1200 media tray.
Figure 1: JCS1200 Media Tray

The media tray is a hot-swappable module that provides two USB connectors for use by the Routing Engines, error LEDs, an ambient air temperature sensor and a pressure sensor for use by the management module, and two CompactFlash bays for CompactFlash disks.
You can order the JCS1200 platform with one or two hot-swappable media trays. The media trays can be installed in media tray bay 1 and media tray bay 2 to provide redundancy.
Each media tray consists of the following components: