SMD SCADA-Mux Statistical Multiplexer

SMD-01, SMD-04, SMD-08, SMD-16, SMD-24, SMD-32

Multiple Port SCADA Multidrop Multiplexer Combines multiple Polling Systems Over One Network

  • Multiplex up to 32 separate polling systems together
  • Each port can have a different protocol and application (DNP, Modbus, SCADA, AMR, etc.)
  • Each port can be set to a different speed
  • Host to remote port speed conversion
  • Multiplex over radios, modems, DSUs, etc.
  • Use for SCADA RTU control, metering, load management, etc.
  • Host ports map 1 to 1 to the remote ports
  • Each host supports up to 63 remote units, each remote may have 1,4,8,16,24, or 32 ports
  • Synchronous or asynchronous composite
  • Internal spread spectrum radio option
  • Operating temperature range of -40 to +70 C
  • Stand-alone, rackmount, or wallmount


Port Specifications
Network Specifications
Operating Modes
Indicators (front panel)
Network Management Port
Network Management Port Commands




The SCADA Multidrop Mux (SMD) is designed for sharing one multidrop radio, modem or DSU system with 2 or more multidrop polling systems. With the SMD, one multidrop network can support multiple protocols and systems, such as DNP, Modbus, etc. RTUs can be polled on a multidrop system at the same time other polling takes place for load management, automatic meter reading, etc. The SMD is 50 to 75% less costly than duplicate and parallel multidrop radio, modem, or digital systems. And that savings is just for the up front purchase cost. After factoring the cost of licensing radio systems, installing and maintaining equipment, savings are even greater.

The composite (or common port) of the mux can be synchronous with speeds up to 128 Kbps, or asynchronous, with speeds up to 115.2 Kbps. Ports can be individually set at speeds up to 57.6 Kbps on smaller units, 38.4 Kbps on larger units. The composite and ports are RS232. The ports can be used with just 3 wires (send, receive and ground) or with full RTS/CTS and Carrier Detect control. RS422 adapters are available for the ports.

In addition to multiplexing polling protocols, the SMD can be used as an Ethernet bridging device, Access Switch, or power control device. For low bandwidth Ethernet applications, Ethernet can be added using DCB’s SCADA Multidrop EtherBridge. The Access Switch function allows terminal control of remote serial device management ports (UPS, radios, meters, etc.) The DCB APS-01 unit provides for a remote power control switch.

The SCADA Multidrop Mux (SMD) sends data from host terminal ports to the remote units as soon as the data comes into the host ports. All the remote SMDs receive the data. The host SMD is also continually checking the remote SMDs to retrieve any data from remote ports. The SMD unit also keeps together blocks of data coming into the ports. This insures that polling protocols such as Modbus RTU will work successfully with the SCADA Multidrop Mux.

Setup of the SMD is simple, using a terminal or PC connected to the management port. Easy to use English command menus are used to set the number of remote drops, the port speeds, port IDs (if desired), the drop number for the remote SCADA multiplexers, sync or async network operation, and control lead timing parameters. The management port can also be used to check system operation, including port activity, link errors, port monitoring, etc. The management port commands are short, simple and comprehensive. Drop SMD multiplexers can be added as transparent devices, activated only when a host SMD is installed. This makes installation much less stressful, since the SMDs can be installed without taking an entire system out of service.

This series includes a single port version. Why a one-port version of a multiplexer? There are sometimes locations in the network with only one of the multiple systems in use. Using a one-port version (mapped to the appropriate host port via configuration) is a cost-effective way to include those locations in the system.

Asynchronous Statistical Multiplexing with SCADA Protocol Compatibility
1, 4, 8, 16, or 32 independent channels
Ports speeds up to 57,600 bps on the 1 and 4 port units, 38.400 bps on larger units Composite speed up to 115.2 Kbps asynchronous, 128 Kbps synchronous
Port Specifications
Data Format
1 Start bit
8 Data bits including parity if used
1 Stop bit
10 Bits total (11 Bit firmware optional)
Rates: 300, 1200, 1800, 2400, 4800, 9600, 19200, 57,600 bps individually selectable per port
Interface: CCITT V.24, RS-232-D
Connectors: RJ-45 (8-wire)
Buffering: 64K dynamically allocated
Port Protocols: Individual ports may use any asynchronous protocol
Network Specifications
Rates: Follows modem clock signals to 128 Kbps synchronous, 115.2 Kbps asynchronous
Interface: CCITT V.24, RS-232-D
Connector: RJ-45 (per EIA/TIA 561 spec for RS-232 in a modular 8 position connector)
Error Correction: Automatic retransmission
Indicators (front panel)
Power, Acitivity, Receive Error, Modem Ready, Port 1 Setup, Loopback
Network Management Port
Interface: CCITT V.24, RS-232-D
Connector: RJ-45 (8-wire)
Can be mapped to Port 1
Network Management Port to terminal cable included
Network Management Port Commands
Show Port Configuration Show Map Show Network Status Change Port Configuration Change Map Change Delay Timeout Configure Network Configure Options Configure Radio Modem Show / Change mux and port IDs Set NMP Password Set Access Port disconnect string Set Access Port prompt Activity Counters Zero Activity Counters Drop Activity Counters Drop Status Test Tools Capture Access Port Monitor Port Tx Monitor Port Rx NMP Parity Ping Drop Power Port Commands Reset Mux Type Repeat Last Command
Power requirements: 120 VAC, 30-43 Watts, Optional (12, 24, 48, 125 VDC or 240 VAC) power supplies available
10 1/4" x 9 3/4" x 2 1/4"
56/64 Kbps internal DSU/CSU ISM Band radio transceiver Dial-up modem

Rear view of 4 port SMD Multiplexer


How to Order

SMD SCADA-Mux Pricing:
SMD-04 4 (async) Port SMD SCADA-MUX Multiplexer $ 995
SMD-08 8 (async) Port SMD SCADA-MUX Multiplexer $ 1695
SMD-16 16 (async) Port SMD SCADA-MUX Multiplexer $ 2195
SMD-24 24 (async) Port SMD SCADA-MUX Multiplexer $ 2995
SMD-32 32 (async) Port SMD SCADA-MUX Multiplexer $ 3695
SMD-01 One 1 (async) Port SMD SCADA-MUX Multiplexer $ 695
SR-DSU4 Internal 56/64 Kbps DSU option for SMD-01 or SMD-04 SCADA-MUX $ 250

Data Comm for Business Inc.
2949 County Road 1000 E
Dewey, Il 61840
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Toll Free: 800-4-DCB-NET
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Email: Contact Page
Fax: 217-897-8023
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