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User Manual
CBM Dual Modem Single Channel Multiplexer





Version 2.0
October, 2000





FCC Information
As per Federal Communications Commission Rules concerning radio frequency emissions, this device complies with FCC Part 15, Subpart J for class A computing devices.

This device generates, uses, and can radiate radio frequency energy and if not installed in accordance with the System Practice, may cause interference to radio communications. It has been tested and found to comply within the limits for a class A computing device pursuant to Subpart J of Part 15 of the FCC Rules designed to provide reasonable protection against such interference when operated in a commercial environment. Operation of this equipment in a residential area is likely to cause interference in which case the user at his own expense will be required to take whatever measures may be required to correct the interference.

Antistatic Precautions
Electrostatic discharge ( ESD ) results from the buildup of static electricity and can cause damage to electronic components. ESD precautionary practices are required when installing, configuring, or repairing this device. Use of a wrist strap is recommended. Do not use conductive tools to change parts or jumper settings in this device.

NEBS Compliance
This Class 2 data communications equipment has been Level 3 NEBS compliance tested and approved under the guidelines specified by the Bellcore GR-63-CORE, and Bellcore GR-1089-CORE Technical References. The CO SAM conforms to the UL Standard for Safety, ANSI/UL 1950, Third Edition.

The manufacturer warrants that this equipment is free from defects in materials and workmanship. The warranty period is five years from the date of shipment. The manufacturer's obligation under this warranty is limited to the repair or replacement of the defective equipment provided it is returned, shipping prepaid, within a reasonable period of time. This warranty shall not apply to equipment that has been subject to accident, misuse, alterations, or repairs not made or authorized by the manufacturer.

This publication and the equipment it describes contain proprietary information. No part of this document may be copied or reproduced in any form without permission from the manufacturer. The information in this document is subject to change without notice. The manufacturer assumes no responsibility for damages resulting from the use of this document, including but not limited to, lost revenue, lost data, or other damages.

Technical Support
For technical support call 1-800-881-8202.












1. Introduction

The Dual Modem Single Channel Multiplexer (DMSCM) provides connectivity redundancy through manual or automatic switch-over in the event of a facilities loss. The I/O card was engineered to be compatible with two Lucent BNS/VCS Datakit trunk cards (T1 and SAMSL). It incorporates (2) internal 56KB DDS modems that are monitored and controlled by an embedded CPU that automatically switches from the primary circuit to the backup circuit in the event of a facilities failure.

The monitor program watches for both loss of carrier and data mode idle (no valid data being received). If the condition is present on the in-service line, the CPU checks the backup line condition and switches from primary to backup. When the primary line failure clears, the CPU will automatically restore the connection to primary. If either the primary or backup line fails, the monitor program will provide a contact closure alarm point for the failing line. This scan point alarm is jumper configurable for normally open or normally closed operation.


  1. Two internal modems provide online/backup redundant functionality.

  2. A three (3) position hardware switch provides:
    1. manual select primary
    2. manual select backup
    3. auto mode(CPU controlled)

  3. Two alarm points are provided to alert Primary or Backup failures. These contact closure points are jumper configurable for normally open or closed operation.

  4. One console port is provided for remote or local access. This allows for system configuration, remote switching between primary and backup lines and system status reports. The port is RS232 9.6 baud 8 bit data 1 stop bit/no parity. The port is password protected and time out protected for added security.

  5. Loop back functions are performed through console port commands and/or manual operation of physical loopback switches on the I/O circuit card.

  6. Default modem operation is 56K baud DDS internal clocking.


2. Product Description

Hardware Specifications


  • CPU operating 16. MHz
  • 20k Flash Memory
  • 128 bytes direct data address space (DATA)
  • 128 bytes indirect data address space (IDATA)
  • 128 bytes serial flash memory to save configuration parameters


  • Two Level-1 Modems connected via leased lines. (non-dialing modems)
  • Operation mode is "56Kbit DSU Internal"

Serial Port

  • 9.6 Kbs, 8-Data , 1-Stop bit, NO Parity.

3-Way default modem selection

  • Lower position (Auto mode): DMSCM card connects Datakit I/O channel to selected "Default Modem" (Primary or Backup). If the default modem fails, or the facility is inoperable the Datakit I/O connection switches over to the Backup modem.

  • Middle position (Forced to Backup Modem): "Default Modem" configuration has no importance. If the Backup Modem fails or the facility becomes inoperable, the Primary Modem can not connect to the Datakit I/O channel.

  • Upper position (Forced to Primary Modem): "Default Modem" configuration has no importance. If the Primary Modem fails or the facility becomes inoperable, the Backup Modem can not connect to the Datakit I/O channel.

    Note: If the remote and local DMSCM cards are in "Auto Mode", the 3-Way switch can be manipulated from either the remote or local site for maintenance and testing purposes.

Reset Button

  • Used for complete HW reset for DMSCM Modems and the Serial Port.


3. Functional Block Diagram

The DMSCM connects the Datakit I/O channel and one of two analog DDS lease lines via the internal modems. The 3-Way toggle switch provides additional control over the modem selection. Only one line can be connected to the channel at any given time.


4. Line Channel Connection Procedures

Line selection procedure

  • Factory default settings use the Primary Modem as the Primary and the Backup Modem as the Backup.

  • A 3-Way hardware switch is provided to change the modem selection. If this switch is moved to either the Middle (Backup Modem) or upper (Primary Modem) position, forced modem selection mode is active. While the manual switch is in either of these two positions the console command MT (modem toggle) will have no effect, the modem manually selected will remain connected to DMSCM. Therefore, if the DMSCM is manually switched to an out of service line the SAM or TRUNK will be inoperative. Manual selection overrides CPU monitoring and selection.

  • Local DMSCM card's "Default Modem" line should be connected to remote DMSCM card's "Default Modem". This means if the local default modem is Primary, the remote location should be connected to its default Primary on the DDS trunk facilities. If cross wiring exists, corrective action should be taken using the modem switch procedure.

  • "Default Modem" switch-over procedure; After logging on to the DMSCM console, type "MS" (modem switch) command. This will switch "Default Modem" selection from Primary to Backup or vice versa. Verify the result with "SH" (show) command.

  • Modem toggle procedure; When both modems are in their Connected and Ready states respectively, the "MT" (modem toggle) command will toggle the connection from "Connected Modem" to "Ready Modem". After a reset the original "Default Modem" selection will be applied. Consecutive "MT" commands will force the connection to alter. NOTE: The "MT" command will only function properly from the Master DMSCM.


5. Console and Modem Connectivity

Serial Port (Console) and Modem Wiring Diagrams

NOTE: The Serial (Console) Port can be connected to a TY12 via an eight wire RJ45 to RJ45 straight through cable to facilitate remote access capability.

Default line selection and wiring



6. DMSCM Toggle Switch, LEDs, and Jumper Configurations

Toggle Switch Operation

The hardware three (3) position toggle switch on the DMSCM will ship in the 'AUTO' position. In this position the default modem will be the 'Primary Modem'. During normal operation the DMSCM in both the remote and local devices should be left on this setting. Auto Operation allows the resident CPU to constantly monitor the condition of the facilities and verify the stability of the connection. Should a modem or line failure occur, the CPU switches over to the Backup resources. This switch-over occurs in less than one (1) second and does not cause a trunk fade. When removed from the 'AUTO' position (into either the Primary or Backup position), the DMSCMs' resident CPU is overridden. The toggle switch should only be taken out of the 'AUTO' position for maintenance and trouble clearing operations. Please refer to the diagrams below for proper toggle switch operation.

This is the 'Normal' or 'Default' Operation of the DMSCM. Both the Local and the Remote Switches are in the 'AUTO' position. This allows the resident CPU to utilize and monitor the Primary facility. In the event of a modem or facility failure the CPU will switch over to the Backup modem and facility.

With one end in 'AUTO' and the other end in 'BACKUP', the CPU is overridden and the DMSCM will default to the Backup facility and modem. This configuration may be employed when the Primary facility is to be taken out of service for maintenance or trouble clearing procedures. NOTE: With one end in 'AUTO' and the other end in PRIMARY, the CPU is again overridden and the DMSCM will default to the Primary facility and modem.

With one end in PRIMARY and the other end in BACKUP, the DMSCM is not operational. Normal operation requires that the toggle switches be left in the 'AUTO' position except for maintenance and trouble clearing purposes.

Status LEDs

Six LEDs are provided on the DMSCM to facilitate visual operational status of both the modems and the facilities. The top three (3) LEDs monitor the status of the Backup facility and modem, while the middle three (3) LEDs monitor the Primary facility and modem. The bottom pair of LEDs indicate which modem/facility is active. Please refer to the diagram and matrix below.

Jumper Configuration

The DMSCM provides two (2) Scan Point Alarm Jumpers. If either the Primary or Backup facility fails, the monitor program on the internal CPU will provide a contact closure alarm point for the failing line. This scan point alarm is jumper configurable for 'normally open' or 'normally closed'. The DMSCM ships with the jumpers in the 'normally closed' position. The jumpers are located on the DMSCM. They are labeled 'JMP1' which is associated with the Primary modem and 'JMP2' which is associated with the Backup modem. There is an additional Timing Jumper that MUST be shorted when the DMSCM circuit card is used in conjunction with a TN1392 T1-Trunk in the SAM. The jumper should be removed when used with any other circuit card. See the diagram below for jumper locations and settings. For Console connectivity to a TY12 module, the DTR Jumper MUST be shorted. Leave open in all other applications.


7. Console, Configuration, and Diagnostic Commands

Console Commands

The DMSCM provides a password protected serial port interface for local or remote console configuration, testing, and status report generation. The. Console Serial Port has an RJ45 type connector and is configurable for 9.6 KB, 8 bit, 1 stop. The port is also 'time out' protected. The following pages contain the user available card control commands. The default password is 'cbm'. It is recommended that the password be changed after the product is installed.

Configuring from the terminal display

Boot screen, Logging on and out and command line

After the DMSCM startup the user may login at the PSWD prompt by entering the initial password 'CBM'.

The screen below is only observed right after pressing the reset button, upon initial power up, or after executing the RESET 'RE' Command. The Version Number and the CBM USA Product ID of the DMSCM are important parameters for trouble reporting and problem resolution with CBM customer service representatives.

The Command Prompt

The "IM1000:" prompt is an indication that the DMSCM is ready for input commands. Invalid commands are responded to by an audible "BEEP" or with a text display describing the cause for the error. The command line display format is shown below.

CP - Change password

Password access is required to configure the DMSCM. Sessions stay active as long as there is keyboard activity. The session will drop in the absence of keyboard activity after 200 seconds. This timing parameter is user configurable. The user is allowed to change the password after a double verification sequence of two identical entries up to 8 characters. The password is not case sensitive and alphanumeric characters are allowed. If the password is correctly typed twice it is accepted and modified Default password is set to CBM when card is shipped.

Quick Start

The DCSCM cards operate in a Master/Slave relationship. Use the SET 'S' command to program the Node side as 'Master' and the SAM side as 'Slave'. Use the MS (Modem Switch) command to set the Primary and Backup modems. The SAM side and the Node side MUST match for proper operation. Use the MODEM 'M' command to set the desired facility timing mode (see the Help Modem Menu 'HM' for options). Verify the settings using the SH (Show) command (see the following page). When the primary modem displays the 'CONNECTED' status, and the Backup modem displays the 'READY' status, the DCSCM is ready for operation. At this point you may download the SAM, provided that the hardware cables and jumpers have been properly configured.

SH - Show DMSCM status

This command shows the current status of all logical and physical entities in DMSCM card which include the Default Modems, Master and Slave Setting, LED(s), Timers, and the Status and Connection Type.

HE- Help request, syntax errors or unrecognized commands

The General Help Menu 'HE' display is shown if an unrecognized command is entered in command line or if the return key is entered with no command.

DCSCM Loopback Commands

Remote Loopback

The DCSCM comes equipped with a resident Remote Loopback Feature that allows the user to test the health of the facility on either of the modems without service interruption. The Remote Loopback Feature is initiated from the Console Command Prompt (IM1000) and executes a data looping routine to determine the status of the facility (see below). If the active line is chosen for the Remote Loopback Diagnostic the DMSCM will query the user and require a YES or NO response to continue so as not to affect any active traffic. After completion of the diagnostic, the DMSCM takes the loop down and returns to normal operation. Use the Help Test 'HT' command to view diagnostic parameters.

CSU/DSU Loopback Commands

CSU/DSU Loopback

The DMSCM CSU/DSU Loopback utilities are to be used with diagnostics resident to the Datakit Node. However, they may also be used when conducting diagnostic routines with the Test Bureau on suspect facilities. Both the CSU and the DSU Loopback commands initiate a loopback condition that directs data AWAY from the initiating device (i.e. A CSU Loopback command executed on the SAM DMSCM will loop the facility back to the Datakit Node). The loopback condition remains in place until manually removed (see below). The CSU Loopback command directs data back prior to entering the resident modem logic. The DSU Loopback Command directs data back after utilizing the modem logic. A CSU/DSU LOOPBACK CONDITION ON THE ACTIVE CIRCUIT WILL INTERRUPT TRAFFIC AND CAUSE A TRUNK FADE. CAUTION SHOULD BE EXERCISED WHEN USING THESE COMMANDS!

DMSCM Loopback Switches

CSU Loopback Switches

The DMSCM is equipped with two (2) toggle switches that can be utilized to initiate a CSU Loopback state. This is the same condition that results from a console initiated CSU Loopback Test. The switches are delivered in the standard operating position, which is to the left and labeled 'NORMAL'. To place the DMSCM in the Loopback Mode, move the desired circuit switch to the right 'LOOPBACK' position. The Looped condition remains until the switch is returned to the 'NORMAL' position. A CSU LOOPBACK CONDITION ON THE ACTIVE CIRCUIT WILL INTERRUPT TRAFFIC AND CAUSE A TRUNK FADE. CAUTION SHOULD BE EXERCISED WHEN OPERATING THESE SWITCHES!

Local Loopback Testing

The DMSCM was designed to utilize the included RJ45 Loopback Plug in conjunction with the Datakit resident SAMTRK diagnostic. The Loopback plug is inserted into the desired modem port and the SAMTRK diagnostic is run in the 'near_dsu' mode. No loopback switches need to be operated and no DMSCM commands are required to execute the SAMTRK Datakit diagnostics. The Loopback plug can be easily manufactured by joining leads 1 to 7 and leads 2 to 8.

Alarm Messages

The DMSCM will upon detection of a facility failure and subsequent switchover generate the following Datakit alarm messages when installed in a CBM Enhanced SAM64. The first Alarm Message will appear only indicating that the Alarm Grid has been activated. The second message will appear every five minutes until the alarm is cleared. NOTE: When the DMSCM is installed in a CBM Enhanced SAM128 only the second Alarm Message will be activated.

Alarm Indicators

Along with the Datakit Alarms, the DMSCM also has an audible and a visual alarm on the front panel of the CBM Enhanced SAM64 and the SAM128.

ALARM NOTES: A Facility Failure will activate the Red FAULT Light as well as activating the Audible Alarm. The Audible Alarm can be silenced by operating the rocker style Cutoff Switch. Doing so will illuminate the Yellow OFFLINE Alarm Indicator.

Error Messages

The DMSCM will report Error Messages on the 'SH' (show status) page (see below).