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GDK-20W DIGITAL WIRELESS KEY TELEPHONE SYSTEM
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Key Service Unit (KSU)
The KSU is a plastic cabinet designed for wall mounting. The KSU contains a MBU(Main Board Unit) and POWER
Transformer and Mechanical parts.
Main Board Unit (MBU)
A Power Supply Circuit is required in the Key Service Unit. The Power Supply Circuit converts local AC power(220~240V
AC @ 50~60Hz) to DC voltages, regulates the voltages, and provides the appropriate DC voltages to the MBU for
distribution to other system components. Three DC outputs are provided : ±5V DC, +30V DC.
The MBU, incorporates, master clock, one alarm detection circuit, one general purpose relay, watchdog circuitry and 4
ports digital terminal interface circuits and 2 ports SLT circuits as well as the system's PCM voice processing and main
micro-processor. And the MBU contains one wireless terminal interface circuit that is used to install one base station to
support 4 simultaneous DECT calls.
The micro-processor is a 16 bit high speed CPU that receives and transmits signaling information from/to other PCBs,
controls feature activation, and PCM time-slot interchange. For digital voice processing, two ROM's contain PCM tone,
gain table, etc.
There are two commonly used slots, SLOT2 and SLOT3, and four fixed slots for extending the system capacity. From
the left side, the SLOT1 is used to install the DVIB/DVIBE. The SLOT2 and SLOT3 are used to install
LCOB2/LCOB/LCOBE/LCOBA/LCOB4 and STIB2 / STIB. The SLOT4 is used to install the PMU basically. The SLOT5 is
used to install the WTIB and the SLOT6 is used to install the MFB.
The permitted terminals are as following.
Keyset: KD-36D, KD-36N, KD-24D, KD-24N
KD/E-36EXE, KD/E-36ENH, KD/E-24EXE, KD/E-24ENH, KD/E-8BTN
LKD-2NS, LKD-8DS, LKD-30DS, etc
DECT terminal: GDC-330H, GDC-335H, GDC-340H
Program Module Unit (PMU)
The PMU is installed to SLOT4 basically and incorporates the system's memory, one internal and one external MOH
ports, Real time clock circuit and two DTMF receivers. Each receiver is time-shared under the control of the system
software.
The LEDs in upper side of the PMU panel indicates system’s power on/off state and data communication state. Also, the
PMU contains 512Kbytes of RAM and 1Mwords of Flash memory.
The RAM associated with the system database and the real-time-clock is protected from power loss by a long life high
energy lithium battery.
Two(2) Flash memory(U1 & U2, 512Kwords respectively) contains the basic system operating software.
Ring Generation Unit(RGU)
The GDK-20W system provides two kinds of ring signals. One is 50Hz sine wave signal generated from power
transformer, another is 25Hz square wave signal from RGU.
The RGU is installed to connector,CN23,of MBU and generates 75Vrms ring signal that can be applied to the two(2)
SLTs simultaneously.
Multi Function Board (MFB)
The Multi Function Board(MFB) Provides a RS-232C interface port with 9 pin connector. The maximum baud rate is
38400bps. The MFB is useful for system maintenance, PC based admin, SMDR print out and local software up-grade.
It is recommended that the RS-232C serial cable whose length is below 10 meters is used.
The MFB includes circuitry for float charging an externally connected 24 volt battery and controls the
operation of the battery back-up circuits. And the MFB will provide system operating voltages from the