The SR-20 sub-rack is a standard 19" x 5.25" frame that can accommodate up to fourteen fiber optic plug-in card slots along with a PSR-1 or PSR-2 power supply.

The SR-20R sub-rack is a standard 19" x 5.25" frame that can accommodate up to eleven fiber optic plug-in card slots along with PSR-1M and PSR-1S power supplies. In the event of Master power supply failure the Slave power supply automatically takes over to supply power to the application cards. A PSR-1M and PSR-1S are required for redundant operation. A PSR-1 or PSR-2 will function properly in an SR-20R, but will not provide redundancy.

SR-20D sub-rack is a standard 19" x 5.25" frame that can accommodate up to 14 fiber optic plug-in card slots. Any one slot accepts the RD-20D Remote Diagnostics card. This configuration allows graphical display of the SR-20 on a remote computer connected via ethernet or RS232. System paramteres of the local rack cards and the remote modules connected to them are displayed in tables below a graphical view of the SR-20 and plug-in cards. Plug-in cards with the model number suffix "D" are compatible with the system.

The PSR-1 is plug-in power supply unit for the SR-20 sub-rack frame. It allows up to 75 Watts of output power to be provided to the application cards. This power supply includes a power selector switch for 115 or 230VAC. The PSR-1 is available as a redundant configuration for use in the SR-20R. A Master power supply PSR-1M is used with an PSR-1S in this configuration.

The PSR-2 is plug-in power supply unit for the SR-20 sub-rack frame. Utilizing state of the art, low noise, switching power supply technology, it allows up to 100 Watts of output power to be provided to the application cards. Over voltage and thermal protection are included in the unit. This power supply includes a universal power input range of 100 to 240 VAC.