The Series 920 through Series 958 systems are housed in a small cabinet. The small rack-mount cabinet contains the system processor unit (SPU), the CIO expander, and the battery backup unit (BBU). The cabinet can also contain various peripherals. If you are working with a Series 922 or a Series 932 system, including the LX and RX models, please refer to HP 3000 Series 922 Family Computer Systems/Operator Hand
book (A1027-90019).
Figure 12-3 Series 920 Through Series 958 Systems
![[Series 920 Through Series 958 Systems]](img/lg122001.gif)
Brief descriptions of the components of Series 920 through Series 958 systems are as follows:
The SPU houses system cards (memory, peripheral, processor) and the power supply.
A channel adapter or precision bus adapter (PBA) connects CIO devices. The Series 948 and 958 systems also connect CIO devices through the Precision Bus Adapter (PBA).
The battery backup unit (BBU) supplies power to memory cards in the event of a power failure.
The operating system resides on the system disk once it has been installed.
The system console is the device designated to send and receive system messages.
One to four disk drives can be contained in the cabinetry.
One digital data storage (DDS) cassette tape drive is contained in the cabinetry.
Several types of page printers and line printers can connected to these systems.
