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The control system of the main unit is composed of the main central processing card (DMPR card) controlling the entire system
and exchanging voice data, the circuit control section (LPR/LC) controlling various telephone lines and the power supply section
(POWER).
DMPR card, LPR/LC and POWER are connected each other through the System BUS (ADDRESS BUS, DATA BUS and CON-
TROL BUS). DMPR card and LPR/LC are under I/O control (I/O Read/Write) by DMPR card.
DMPR card controls LPR which have a microprocessor by the lnter-Microprocessor Communication System supported by
ASIC. Those are, DMPR card and LPR exchange controlling messages through bi-directional buffer and CPU controls LPR so
that it can manage multiple telephone lines. Since LC does not have a microprocessor, it is completely controlled through ASIC
from DMPR card. 
I/O address for LPR access is fixed for each free slot. CPU discriminates the sort of LPR through the inter-processor communi-
cation system.
POWER detects the voltage drop of the AC input and the DC output and transfers it to DMPR card.

This card is the main control section of main unit. It controls all the cards mounted on the free slots, and communication of RS-
232C ports. DLC port of onboard is controlled. 
There are two LED (BATT ALARM, SD ACCESS), one SD card slot, one push switch, one slide switch, one USB port, one RS-
232C connector,two RJ11 connectors(DLC),one RJ45 connector (MOH and EPG) in the front of DMPR card. BATT ALARM LED
light red if the output of the lithium battery in DMPR card is set to about 2.8V or less. During access to SD card, it green-blinks
or SD ACCESS LED light and blink. Enclosed SD card is used for SD card slot on a main part, putting in. The main program is
stored in SD card. It connects with PC and a USB port is used for a maintenance or a system setup. The external sound source
for BGM or suspension sound is connected to a RJ45 connector. A speaker with amplifier is connected to external paging at
RJ45 connector. Light Emitting Diode (RUN indicator, ALARM indicator) arranged at the main part upper part is directly con-
trolled from DMPR card, and shows the state of a system of operation. 
This control circuit executes the control signals for the exchange process, and this card is composed of the following
(A) 32bit CPU (32bit data bus)
(B) SDRAMs, SRAMs
(C) Flash memorys
(D) Lithium Battery for back-up of clock IC and Static RAMs

BB (back board) is the mother board of the basic shelf. This board connects each card/unit (POWER, DMPR card, and optional
service cards) together.

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This unit is switching regulator power supply and supplies DC voltages to DMPR card, and optional card (free slot). PSU (power
supply unit) has two outputs (41V, 15V). 15V output is supplied only in DMPR card and option card. Other outputs are mainly
used as an object for the electric supply to a terminal. 

This circuit consists of the following components and removes the exogenous noise or the noise generated at power supply.
C1, C2: normal mode filter (X condenser)
L1, L2: common mode noise filter
C3, C4: common mode noise filter (Y condenser)

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This circuit consists mainly of the following components and performs DC-AC conversion.
D1: Diode Bridge
C5: Primary Smoothing Condenser

As the main component of this circuit, Z1 protects against exogenous noise such as lightning surge.
Z1: Varistor

Immediately after AC input applies voltage, the following components control inrush current to the Smoothing Condenser.
NTC1, NTC3: thermistor

This circuit consists of the following components and detects AC input.
Main components: D81,D82,R80-R95,Q80,Q81,Q82,PC80
AC voltage commutates through D81, D82.
When AC voltage is over the threshold, Q80, Q81, and Q82 are switched ON to allow AC Detection Circuit to transfer AC input
status to the secondary side AC alarm signal delivery section through PC80

This section describes the main converter circuit which insulates the primary DC voltage and converts the voltage to a Secondary
voltage (41V output).

This main converter consists of the following components; Isolated, and Self-excited Pseudo Resonance Type Converter.
Q1: main switch FET
T101: isolation transformer
IC1: IC controls Q1
PC1: device for transfer control secondary side
Other peripheral circuit

Secondary side output condition is transferred by PC1 to the primary side.
Q1 is switched to ON/OFF in IC1 to control the secondary side voltage.

T101: The output of this isolation transformer is 41V, and is the power supply for output voltage in section 3.

This output consists of the Rectification Smoothing Circuit of D101, C101.
This is the output described in section 3, 15V and 41V output for power supply, and also for battery output as described in
section 4.

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The main converter latch circuit works to prevent output voltage from reaching an abnormally high state.
This circuit uses mainly the latch function of IC1.
When secondary side protection circuit reaches an abnormal state (section 6 protection circuit), the signal is sent to primary side
through PC50.
The main converter latch circuit then works to stop the operation.
To release the latch status, release abnormal state, then switch the AC input OFF and leave for over 60 seconds before restart-
ing AC input again

This section describes the operation of the circuit that converts the main converter output to 15V and 41V.

This separately-excited depressor chopper converter consists mainly of IC202, D204, L201, C209, C210, R212-R214.
Input power supply is 41V output of the Main converter described in section 2.
15V output is supplied by the ON/OFF switching action of IC202, D204 and Smoothing Circuit of L201, C209, C210.
Output voltage is set by the resistance rate of IC202, R212-R214.
Oscillating frequency IC202 is 300kHz(typ).

Operation is protected the IC202 internal Overcurrent Protection Circuit.