Toshiba Strata Dk14, Dk40i, Dk424 General Description Manual

							Universal Slot PCBs
Console PCBs
Strata DK General Description    5/9937
©DK40i
 – a K5RCU or K5RCU2 must be installed in the Base KSU to interpret DTMF tones 
transmitted by devices connected to the standard telephone circuits.
©DK424
 – an RRCS must be installed on the common control unit to interpret the DTMF 
signals for devices connected to the standard telephone circuits.
48V Loop Voltage (R48S)
The optional R48S unit can be connected to the RSTU2 or RDSU, and, by creating 48V loop 
voltage instead of 24V, can extend the maximum possible loop length of standard telephone 
circuits (including the resistance of the phone) from 600 ohms to 1200 ohms, allowing standard 
telephones to be connected farther from the system.
By using this unit, a less expensive type of off-premises lines can be used (see Table 23 on Page 
40). 
Console PCBs
Attendant Console Interface Unit (RATU, DK424 only)
The RATU can support four attendant consoles. Multiple consoles enable automatic load-sharing 
on a rotation basis from a central call queue, increasing call handling efficiency. The RATU PCB 
in the Strata DK424 system cabinet connects to the PC Attendant Console Interface (RATI) via 
two pair of wires.
RATU is only available for systems operating with RCTUBA/BB, RCTUC/D or RCTUE/F 
common control units. One RATU is available per system to support a maximum of four Attendant 
Consoles per system with RCTUC/D or RCTUE/F, two with RCTUBA/BB, (any combination of 
PC or conventional consoles).
CO Line PCBs
A summary of Strata DK station, CO line PCBs and feature subassemblies are listed in Table 23 on 
Page 40.
Caller ID Interface Unit (RCIU2)
The RCIU2 is required, along with an analog ground/loop start CO line PCB, to provide the Caller 
ID feature. Caller ID is also known as CLID and is available at extra cost per line from the local 
Telco. It is sometimes known as a CLASS feature.
Each RCIU2 circuit receives and decodes telephone number and name information sent from the 
calling CO. Caller ID is available on analog loop start lines and analog ground start lines only. An 
RCIU2 circuit must be available with each RGLU2, RCOU/RCOS, PCOU or KCDU2 circuit that 
is to receive Caller ID. Built-in gas tubes help protect each RCIU2 circuit from lightning surges.
An RCIS subassembly PCB can be installed onto the RCIU2 to provide four additional Caller ID 
circuits.
Caller ID Interface Subassembly (RCIS)
The RCIU2 comes equipped with four Caller ID circuits; an RCIS subassembly PCB can be 
installed onto the RCIU2 to provide four additional Caller ID circuits. Hence, an installed RCIU2/
RCIS can provide a maximum of eight Caller ID circuits per cabinet slot. Built-in gas tubes help 
protect each RCIU2/RCIS circuit from lightning surges.  
						

							Universal Slot PCBs
CO Line PCBs
38Strata DK General Description    5/99
Loop Start CO Line Interface Unit (RCOU)
The RCOU in its basic configuration has four analog loop start CO line circuits, connecting to the 
public telephone network. 
Each RCOU line can be programmed for DTMF or Dial Pulse signaling and has a switch to control 
potential excess volume that can be created by a nearby PBX or CO. 
An optional RCOS subassembly can be attached to the RCOU for four more loop start lines. Each 
line can be programmed for DTMF or Dial Pulse signaling. Built-in gas tubes help protect each 
circuit from lightning.
Loop Start CO Line Interface Subassembly (RCOS)
The RCOS can be attached to the RCOU to provide four additional analog loop start CO line 
circuits. Each RCOS line has all of the features that are available with the RCOU lines.
Ground/Loop Start Interface CO Line Interface Unit (RGLU2)
The RGLU2 provides four analog CO line circuits which can be configured individually for 
ground start or loop start. Ground start should be used for applications requiring disconnect 
supervision, such as AA/Voice Mail, or ACD.
The RGLU2 also provides ring detection, dial outpulsing, Hold, and CO line flash signal. Each 
RGLU2 line can be programmed for DTMF or Dial Pulse signaling and has a switch to control 
potential excess volume that can be created by a nearby PBX or CO. Built-in gas tubes help protect 
each circuit from lightning.
Direct Inward Dialing Interface Unit (RDDU)
The RDDU provides four analog DID lines, each of which is assigned a single office code along 
with a block of extension numbers. Each extension number is programmed to ring a [DN] selected 
in system programming. This enables calls over the same line to be routed to different stations. 
Each DID line can be set for either Wink Start or Immediate Start. DID lines can also support 
DNIS and/or ANI. An optional K5RCU or K5RCU2 (DK40i) or RRCS (DK424) tone receiver 
PCB is required for DTMF DID operation. Rotary DID signaling ability at 20 pps is a standard 
feature. An external protector is required for each line.
Tie Line Unit (REMU)
The REMU has four analog circuits for E & M Type I or Type II signaling, Immediate Start or 
Wink Start Tie lines. A choice between 2- or 4-wire transmission is available as a jumper-plug 
option.
Tie lines can also support DNIS and/or ANI. An optional K5RCU or K5RCU2 (DK40i) or RRCS 
(DK424) tone receiver PCB is required for DTMF Tie operation. An external protector is required 
for each line. REMU Tie lines are two-way and can be used for incoming and outgoing calls.
T1/DS-1 Interface Unit (RDTU2) (DK424 only)
The RDTU provides either 8, 16 or 24 digital voice channels that can be individually configured 
for ground start CO line operation, loop start CO line operation, DID/DOD line operation (with 
hookflash) or Tie line operation. The number and type of channels for each RDTU installed is 
assigned in system programming.  All RDTU line types are two-way and can be used for incoming 
and outgoing calls.
Any RDTU, DID/DOD, or Tie channel can be configured in system programming to receive DNIS 
and/or ANI information from long distance carriers. 
						

							Universal Slot PCBs
CO Line PCBs
Strata DK General Description    5/9939
The RDTU is available for systems operating with a RCTUBA/BB, RCTUC/D or RCTUE/F 
common control unit. The RDTU normally requires the installation of a Channel Service Unit, 
which is not supplied by Toshiba. RDTU T1/DS-1 digital voice channels can be configured for SF 
or ESF format and either AMI or B8ZS line coding (see Table 23).
The new RDTU2, installed in a DK424 Release 4.0 system, supports the hook flash capability. 
“SuperTrunk” requires hook flash operation on T1 two-way DID/DOD lines. The RDTU1 can be 
upgraded to support hook flash.
In most locations within the U.S., network connection using RDTU2 requires a dealer-supplied, 
UL-listed external CSU or in Canada, a CSA-certified CSU.
ISDN Primary Rate Interface Unit (RPTU) (DK424 only)
The Primary Rate Interface Unit is a 24-channel PRI card, which provides 1 data (control) channel 
and 23 bearer channels (available in Release 4.0). All B channels appear and program as CO lines 
in the DK424 system and can be individually configured for local service, FX, WATS, DID, Tie, 
etc., service operation. Network connection using the RPTU requires a dealer-supplied, UL-listed, 
external CSU in most locations in the U.S. In Canada, the CSU/DSU must be CSA certified.
The RPTU is supported by the RCTUBA3/BB4, RCTUC3/D4 and RCTUE3/F4. See “ISDN 
Primary Rate Interface (PRI)” on Page 73 for more information.
ISDN S/T-type Basic Rate Interface Unit (RBSU)
The Basic Rate Interface (BRI) Unit provides two BRI S/T circuits. Each circuit provides two 
simultaneous voice and/or data connections with a single interface. BRI uses the 2B+D 
transmission format which is defined as two 64-kbps bearer channels and one 16-kbps data 
(control) channel. The D channel carries call setup control data. 
The RBSU BRI circuits can be connected to ISDN BRI network lines and/or ISDN S-type 
Terminal Equipment (TE-1) or Terminal Adapters (TA) on the station side. 
The RBSU/RBSS BRI circuits that are configured for the station side provide a passive bus that 
enables up to two TE1 and TA devices to be connected to one BRI circuit. When multiple TE1 and 
TA devices are installed on a singled RBSU/RBSS BRI circuit, the devices must share or contend 
for that circuit’s two B channels.
A maximum of two simultaneous voice and/or data calls are allowed between all devices 
connected to the same BRI circuit. The contention rule for the two BRI B channels is first come, 
first serve. Network connections using BRI S/T type interface also require a dealer-supplied, UL-
listed, external Network Terminal (NT-1) device. In Canada, the NT-1 must be CSA certified.
NoteRBSU/RBSS will be available with DK424 and DK40i Release 4.1.
Basic Rate Interface Subassembly (RBSS)
The RBSS attaches to the RBSU to provide two additional BRI S/T type circuits that can be 
used for station-side connections only. An RBSU with the RBSS subassembly provides four 
BRI circuits in one card slot.
RBSU/RBSS stations can be voice and/or data devices, such as ISDN telephones and Terminal 
Adapters, that support the standard S-type interface. Each RBSU/RBSS circuit provides two B 
channels, plus one D channel and reduces the system’s basic capacity by two station ports and 
two CO lines. See “ISDN Basic Rate Interface (BRI)” on Page 73 for more information.
NoteRBSU/RBSS will be available with DK424 and DK40i Release 4.1. 
						

							Universal Slot PCBs
Summary of PCBs and Subassemblies
40Strata DK General Description    5/99
ISDN U-type Basic Rate Interface Unit (RBUU) (DK424 only)
The Basic Rate Interface Unit provides two Basic Rate Interface (BRI) “U” circuits. Each circuit 
provides two simultaneous voice and/or data connections with a single interface. BRI uses the 
2B+D transmission format which is defined as two 64-kbps bearer channels and one 16-kbps data 
(control) channel.
NoteRBUU/RBUS will be available with Release 4.2.
Basic Rate Interface Subassembly (RBUS)
The RBUS attaches to the RBUU to provide two additional BRI “U” circuits that can be used to 
connect to Network BRI lines and/or station-side connections only. An RBUU with the RBUS 
subassembly provides four BRI “U” circuits in one card slot.
RBUU/RBUS stations can be voice and/or data devices, such as ISDN telephones and Terminal 
Adapters, that support the standard U-type interface. Each RBUU/RBUS circuit provides two B 
channels plus one D channel and reduces the basic system capacity by two CO lines and two 
station ports. See “ISDN Basic Rate Interface (BRI)” on Page 73 for more information.
Enhanced 911 CAMA Trunk Interface Unit (RMCU/RCMS) (DK424 only)
The RMCU/RMCS PCBs provide up to four CAMA trunk circuits. The RMCU/RMCS eliminates 
the need for connection of adjunct terminal adapter equipment to E911 CAMA trunks. Available 
for DK424 in Release 4.0. Also, see note below RCMS.
CAMA Trunk Subassembly (RCMS) 
One RCMS subassembly attaches to the RMCU to provide two CAMA trunk circuits. A second 
RCMS can be added to provide four CAMA trunk circuits. Available in a future release.
NoteThe RCMS is ordered separately from the RMCU, but it must be installed on the RMCU 
to provide CAMA trunk interface.
Summary of PCBs and Subassemblies
Table 23 provides a summary of the universal slot PCBs and available subassemblies.
Table 23 PCB Circuits, Interface Options and Connectors 
PCBSubassemblyCircuitsInterface OptionsConnector
RPTU(DK424 only)
1 circuit/ISDN PRI 
(23 B channels/1 D channel)POTS
FX
Tie (senderized)
Tie (cut through)
OUTWATS (intra-LATA)
OUTWATS (inter-LATA)
InWATSRJ48C or RJ48X
ISDN TIA-568A
RBSU 2 ISDN BRI S/T point circuits (NT 
or TE). Each circuit is 2B+1D. 
(Host for the RBSS)Network and/or station side RJ45, ISDN TIA-568A
attaches to 
RBSURBSS2 ISDN BRI, S point circuits (2B+D 
each)Station side only
 1 RBSS subassembly per RBSURJ45, ISDN TIA-568A 
						

							Universal Slot PCBs
Summary of PCBs and Subassemblies
Strata DK General Description    5/9941
RBUU(DK424 only) 2 ISDN BRI, U point 
circuits (2B+D each). Host for the 
RBUS. (Release 4.2)Network and/or station side RJ45, ISDN TIA-568A
attaches to 
RBUURBUS2 ISDN BRI, U point circuits 
(2B+D each) subassembly for the 
RBUU. (Release 4.2)Network and/or station side
1 RBUS subassembly per RBUU.RJ45, ISDN TIA-568A
RDTU2 Applies to DK424 only.
1~8, 1~16, or 1~24 channels 
(lines), depends on system 
programmingLoop start lines
Ground start lines
Tie lines (wink or immediate)
DID/DOD lines (wink or immediate)2-pair amphenol
RJ48M
(All PCB amphenol 
connectors are female)
RMCU2 E911 CAMA circuits with the 1 
RCMS or 4 with 2 RCMSsE911 CAMA lines
RJ11C modular
attaches to 
RMCURCMS2 E911 CAMA circuitsUp to 2 RCMSs per RMCU for 4 
CAMA lines max.
REMU 4 Tie line circuitsE&M Tie lines
2- or 4-wire transmission
Type I signaling
Type II signaling
Immediate start
Wink start REMU (8-wire modular jack)
2- or 4-wire/type I or II
KCDU(DK40i only)
2 CO line circuits/
4 digital telephone circuitsCO loop start lines
Digital circuits same as PDKU, 
except no DDSSRJ14C modular (CO Line 
circuits)
25-pair amphenol (digital 
phone circuits)
RCOU4 CO line circuits (lines)
With RCOS:
8 CO line circuits (lines)CO loop start lines
RJ14C modular
attaches to 
RCOURCOSProvides four additional Loop 
Start CO lines. 1 RCOS subassembly per RCOU
RCIU24 circuits
With RCIS: 8 circuitsLoop or Ground Start Lines with 
Caller ID. Requires: RCOU, RGLU2 
or PCOU
RJ14C modular
attaches to 
RCIU2RCISUsed with RCOU/RCOS, PCOU, 
and RGLU2 CO line PCBs to 
provide 4 Caller ID circuits.1 RCIS subassembly per RCIU2
RDDU4 DID circuits DID Lines RJ14C modular
RGLU24 line circuits  Loop or ground start lines RJ14C modular
PIOU, 
PIOUS, 
PEPU, 
RSSUA PIOU or PIOUS can use an 
IMDUACD/SMIS (DK424 only, except 
RCTUA)
SMDI for Voice Mail
SMDR printer or call accounting 
machine
PC or maintenance terminal (local 
or remote)25-pair amphenol (PIOU or 
PEPU)
Spring clip terminal (PIOUS) 
Two 3-pair modular (TTY/
SMDR/SMDI/SMIS)
(All PCB amphenol 
connectors are female)
attaches to 
PIOU and 
PIOUSIMDUProvides remote maintenance 300 
bps or 1200 bps full-duplex modem 
for DKAdmin or DKBackup. 1 per 
PIOU/PIOUS. None
Table 23 PCB Circuits, Interface Options and Connectors (continued)
PCBSubassemblyCircuitsInterface OptionsConnector 
						

							Universal Slot PCBs
Summary of PCBs and Subassemblies
42Strata DK General Description    5/99
RSTU28 standard telephone circuitsStandard telephones
Voice mail ports
Off-premises stations
Other similar devices
Alternate BGM source
Auto Attendant digital announcer
Message Waiting lamp (RSTU2 
only)
Fax machines
ACD Announcer
Strata Airlink wireless telephones25-pair amphenol
(All PCB amphenol 
connectors are female)
attaches to 
RSTU2 and 
RDSUR48S48 volt circuit for up to 8 standard 
telephone circuitsOptionally interfaces to the RSTU2 
and RDSU to extend loop length of 
standard telephones from 600 
ohms to 1200 ohms.None
RDSUWithout RSTS:
2 standard telephone/
4 digital telephone circuits
With RSTS:
4 standard telephone/
4 digital telephone circuitsDigital: same as PDKU, except no 
DDSS console
Standard: same as RSTU 
(standard Message Waiting not 
available)25-pair amphenol
attaches to 
RSTU2 and 
RDSURSTSProvides two additional standard 
telephone circuits1 maximum per RDSU None
PESU2 standard telephone circuits/
4 electronic telephone circuits 
(standard/electronic telephone 
ports)Standard: same as KSTU2
Electronic: same as PEKU, except 
PESU does not support HDSS 
console25-pair amphenol
RATU(DK424 only)
4 PC attendant PC console 
circuitsPC attendant console
Conventional attendant console25-pair amphenol
PDKU28 digital telephone circuitsDigital telephones (with or without 
RPCI-DI, DVSU, DADMs, or digital 
cordless telephone)
Stand-alone digital cordless 
telephone
DDSS console
PDIU-DS
DDCB25-pair amphenol
Stratagy DK2, 4, 6, or 8 VM ports
All of the above Stratagy DK 
systems use 8 station ports in the 
DK40i and DK424 softwareNone None
PEKU8 electronic telephone circuitsElectronic telephones
HDSS console
Alternate BGM source
EOCU PCB for OCA
External conference amplifier
HDCB25-pair amphenol
(All PCB amphenol 
connectors are Female)
Table 23 PCB Circuits, Interface Options and Connectors (continued)
PCBSubassemblyCircuitsInterface OptionsConnector 
						

							Universal Slot PCBs
Option Interface PCBs
Strata DK General Description    5/9943
Option Interface PCBs
For a list of optional interfaces, see Table 24 (DK40i) and Ta b l e  2 5 (DK424).
Option Interface Unit (PIOU)
The PIOU provides interfaces for Paging (Amplified, Unamplified, and Zone), SMDR, SMDI for 
Voice Mail integration, SMIS for ACD, DKAdmin Interface for on or off-site maintenance, an 
Alarm sensor, and a Remote Maintenance Modem subassembly (IMDU) that allows the system to 
be programmed from an off-site DKAdmin PC.
©DK40i
 – the PIOU PCBs three-watt or non-amplified 600 W paging output is not used since 
paging is supported by the Base KSU paging interface.
attaches to 
PEKU or 
PESUEOCUProvides Speaker OCA path for 8 
circuits on PEKU or 4 circuits on 
PESU. (Handset OCA is not 
available on EKTs.)1 for PEKU or PESU that supports 
Speaker OCA
RSIU
(DK424 only)Up to 4 interface ports when 
installed with the optional RSIS or 
RMDS piggy-back PCBs.ACD/SMIS
SMDI for voice mail
SMDR printer or call accounting 
machine
PC or maintenance terminal (local 
or remote)One 3-pair modular (TTY/
SMDR/SMDI/SMIS)
attaches to 
RSIU
RSIS, RS-232 
interface
RMDS
(Modem/
RS-232)
(DK424 only)Up to 3 RSISs
...or 
1 RMDS and 
2 RSISs per RSIUProvides up to four interface ports 
(RS-232 and modem) for system 
interface with:
RMDS (1200 or 2400 bps)
Voice Mail SMDI
ACD/SMIS
SMDR
Local or Remote Maintenance for 
DKAdmin or DKBackup PC.One 3-pair modular per 
RSIS (RS-232), RMDS 
(Modem/RS-232)
RWIU
4 RJ11 jacks to support 4 Strata 
AirLink Integrated Base StationsDigital Wireless Handsets: same as 
PDKU, except no DDSS console, 
Stand-alone cordless telephone, 
PDIU-DS, or DDCBNone
Table 23 PCB Circuits, Interface Options and Connectors (continued)
PCBSubassemblyCircuitsInterface OptionsConnector 
						

							Universal Slot PCBs
Option Interface PCBs
44Strata DK General Description    5/99
©DK424
 – the PIOU provides two-relay contact pairs. One of the contact pairs can be set for 
control of a customer-provided door lock or control of a MOH source. The other relay pair can 
be configured to mute BGM while the page feature is being activated or for the Night Relay 
function.
Simplified Option Interface Unit (PIOUS)
The PIOUS has most of the PIOU’s features, including SMDR output and the TTY output port 
interface and IMDU. It also provides flexible relay contacts and an Unamplified Page output. It 
does not provide Amplified or Zone Paging.
Remote Maintenance Subassembly (IMDU)
The IMDU is an optional modem that connects to a PIOU or PIOUS to link the system to off-site 
programming and maintenance equipment, such as a DKAdmin PC. The IMDU has an internal 
maintenance channel and does not require a dedicated CO line or station port. Data transmission 
speed can be set at 300 or 1200 bps full duplex.
External Page Interface Unit (PEPU)
The PEPU is a reduced version of the PIOU and PIOUS, providing most of the Paging and Relay 
Contact options offered by these other optional PCBs.
Table 24 DK40i Interface PCB Options
Interface Options1
1. Amplified page output (single zone, 3 watts, 8 ohms) on the PIOU and PEPU is not available on the DK40i.
RSSUPIOUPIOUSPEPUTSIUDK40i Base 2
2. These functions are standard (built-in) to the DK40i Base KSU.Zone page interface (unamplified, 4 zones)
X
Unamplified page output (single zone, 600 
W, 
duplex)X
Night transfer or Music-on-hold control relayXXX X
Door lock or external amplifier control relayXXXX
IMDU disables TTY output when piggy-backed 
onto PIOU or PIOUS cardsXX
Remote Maintenance using customer-provided 
external modem, StrataControl and/or DKAdmin 
PC (requires TTY output port)
XXXX
SMDR output (RS-232/6-wire modular connector)XX X
Alarm sensorXX
Voice Mail SMDI (requires TTY output port)XXX X 
						

							Universal Slot PCBs
Option Interface PCBs
Strata DK General Description    5/9945
Single Serial Interface Unit (RSSU)
The RSSU contains one RS-232 serial port for connecting an SMDI, SMIS processor, DKAdmin/
DKBackup PC or external modem. 
The RSSU provides a cost-effective alternative to the PIOU or PIOUS when only one other serial 
I/O port is needed, or when the other features of the PIOU or PIOUS are not required. The RSSU 
has a fixed speed of 1200 bps. It does not support SMDR, or the IMDU or RMDS modems. 
©DK40i
 – one optional RSSU maintenance interface PCB can be used for connecting a 
maintenance PC or external modem (local or remote) to the DK40i.
©DK424
 – a maximum of three RSSU cards can be supported per DK424.
Table 25 DK424 Interface PCB Options
Interface OptionsRSSU1PIOU1PIOUS1PEPURSIU/
RSIS1
Zone page interface (unamplified, 4 zones)X
Unamplified page output (single zone, 600 ohms, duplex)XXX
Amplified page output (single zone, 3 watts, 8 ohms)XX
Night transfer or Music-on-hold control relayXXX
Door lock or external amplifier control relayXXX
Alarm SensorXX
Remote maintenance modem subassembly (IMDU or RMDS) 
(disables TTY output when they are piggy-backed onto the 
PIOU/PIOUS or RSIU/RSIS cards)
2
X(IMDU)X(IMDU)X(IMDU)
Remote Maintenance using customer-provided external 
modem (requires TTY output port)2XXXX
SMDR output (RS-232/6-wire modular connector)X3X3X
MIS for ACD (requires TTY output port)2, 4XXXX
Voice Mail SMDI (requires TTY output port)2XXX X
StrataControl and/or DKAdmin PC (requires TTY output port)2XXXX
1. PIOU, PIOUS, and RSSU each provide one TTY port which can be flexibly programmed for the features marked with X. 
RSIU/RSIS can provide up to four flexible TTY/SMDR ports.
2. Maintenance modem, ACD/SMIS, Insight DK, Voice Mail, SMDI and DKAdmin PC Interface each require a separate TTY 
output. PIOU, PIOUS, and RSSU provide one TTY output each. RSIU with RSIS PCBs provides up to four TTY outputs.
3. SMDR output will function simultaneously on the same PIOU or PIOUS with one of the following: DKAdmin, remote 
modem, SMIS for ACD, Insight DK, or SMDI features.
4. Insight DK, Call Center Viewer and SMIS for ACD requires that the system processor (RCTU PCB) must be equipped with 
an RKYS3 or higher feature key. 
						

							Universal Slot PCBs
Option Interface PCBs
46Strata DK General Description    5/99
Serial Interface Unit (RSIU, DK424 only)
The RSIU provides up to four interface ports that allow the Strata DK424 system to connect to the 
following:
©Voice Mail system with RS-232 SMDI
©ACD/SMIS system or Call Center Viewer
©SMDR printer or call accounting machine
©DKAdmin/DKBackup running on a PC as a maintenance terminal (locally or remotely)
The RSIU, which comes standard with one port, can be equipped with up to three more optional 
RS-232 ports (total of four RS-232 ports). The Single Interface Subassembly (RSIS) piggy-backs 
onto the RSIU PCB to provide the optional ports. One of the serial ports can be an internal modem. 
An optional 2400 bps built-in Modem Subassembly (RMDS) can be added onto the RSIU.
The maximum allowed combined speed of all four channels is 9600 bps. All four channels of the 
RSIU connect directly to the RCTU processor via a short ribbon cable. The RSIU must be 
positioned in the first universal slot of the Base Cabinet.
RMDS (DK424 only)
The optional RMDS modem mounts on an RSIU and can function either as a remote maintenance 
modem to provide the same functions as the IMDU or as a direct RS-232 link to a DKAdmin/
DKBackup PC COM port.
The function of the RMDS is set in system programming. Data transmission speed for the built-in 
modem function can be set at 1200 bps or 2400 bps via system programming.