Ricoh A250 Service Manual page 415

The basic fax unit consists of two PCBs: an FCU and an NCU.
The FCU controls all the fax communications and fax features, in cooperation with
the base copier's main board, the BiCU. The NCU switches the analog line
between the fax unit and the external telephone.
Fax Options
1. EXFUNC board: JBIG compression becomes available. In addition, this
expands the system's SRAM capacity to hold programmed telephone numbers,
communication records, etc.
2. PC fax expander: Class 2 fax communication from a PC and local printing from
a PC fax application become available (PC fax application required). Also, local
scanning from the machine's scanner using TWAIN API becomes available
(CFM Twain driver required).
3. ISDN unit (Europe model only): This allows the fax unit to communicate over an
ISDN (Integrated Services Digital Network) line.
4. EXMEM board: This expands the SAF memory capacity. Also, this expands the
page memory capacity to enable 400 dpi communications.)
1.3.2 POWER DISTRIBUTION AND CONTROL
The FCU power is supplied from the base copier's BiCU (+24V, +12V, -12V, and
+5V). Refer to the base copier's service manual for details.
1.3.3 MEMORY BACK-UP
The system parameters and programmed items in the SRAM on the FCU and the
EXFUNC board are backed up by batteries (long-term backup), in case the base
copier's main switch is turned off.
The SAF memory (DRAM) on the FCU and the EXMEM board are backed up by
rechargeable batteries for 1 hour.
SM
OVERALL MACHINE CONTROL
1-7 A250