PSU - Poll Sharing Unit for polling SCADA networks

Asynchronous Poll Sharing Unit for polling SCADA networks

  • Shares multiple hosts and protocols
  • Resolves host port contention
  • Asynchronous serial RS232 ports
  • RS422 port interface converters available
  • Port speeds from 1200 to 38,400 bps
  • Four Host ports, 4 Device ports
  • Optional modem for host backup port
  • Each port can be set to its own unique speed
  • Dedicated setup port
  • Buffered Host ports, up to 1000 bytes/poll
  • Buffered combiner mode, optional RTS/CTS mode
  • Per port poll timeout, adjustable to 30 seconds
  • Per port inter-message timer of 5 to 1000 ms
  • Option to control sharing with RTS/CTS
  • Map Host ports to any one or more Device ports
  • Poll response goes only to port that initiated the poll
  • Use to mix protocols from up to four different Hosts over one to four networks
  • Industrial temp operation, -40´‚░ to +75´‚░ C
  • 120, 220 VAC, 12, 24, 48 and 125 VDC power options


Indicators (front panel)
Data Port

Download the Manual


How To Order

The Poll Sharing Unit makes it possible to share up to four polling host computers to as many as four different device ports, connecting to four or more different networks. Networks can be private line, phone company lines, wireless networks, or any combination of networks. The Poll Sharing Unit uses RTS/CTS or buffering and timeouts to resolve contention between the multiple host computers.

The DCB Poll Sharing Unit has four Host ports and four Device ports and optional modem for host port backup. Each port can be set to a different speed, from 1200 to 38,400 bps (port to port speed conversion). The ports are RS232 async. RS422 port interface converters are available.

Polls coming into a Host port are sent out one or more of the four Device ports, mapped by the user on a per port basis. For example, polls coming in Host port 1 may be mapped to all 4 Device ports, while on Host ports 2, 3 and 4, data is mapped to a single Device port.

The Poll Sharing Unit has a per Host port poll timeout and a per Host port inter-message timeout. Polling data coming in a Host port is sent to the selected Device port(s). Any polls coming in on other Host ports are buffered until the first poll out is answered or after the poll timeout expires. Only one Host port at a time may send a poll out a Device port.

Another method of selecting ports is using RTS/CTS RS-232 control leads on the Host ports. The PSU constantly scans all ports for Request to Send (RTS). When RTS is asserted on the Host port, the Poll Sharing Unit returns CTS to the host computer, allowing it to send out a poll. The poll is sent out the mapped Device ports. No other Host computer port will get CTS from the Poll Sharing Unit until the first Host port gets a poll response back from a Device port, or the poll timeout expires.



Indicators (front panel)



Data Port


Rear view of PSU



Order the PSU-08 and any optional power supply you need. Due to the complex nature of SCADA systems,
we recommend that you discuss your application with one of our technical sales people before ordering.

Need it fast?  Buy on-line or call toll free 800-432-2638!

Item Number Description Price Buy Now!
PSU-08 PSU w/ 4 host and 4 device ports, 100-250VAC powered $ 1195 Qty:
9501034Optional 12 VDC (9-18 VDC) power supply in place of standard power supply $ 75 Qty:
9501025Optional 24 VDC (19-36 VDC) power supply in place of standard power supply $ 75 Qty:
9501024Optional -48 VDC (36-72VDC) power supply in place of standard power supply $ 75 Qty:
9501029Optional 125 VDC power supply in place of standard power supply $ 125 Qty:
BPF-125VDCOptional 220-240 VAC power supply in place of standard 120VAC power supply
(specify Country)
$ N/C Qty:
RK-8/16 19" wide rack mount shelf/bezel $ 60 Qty:

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Dewey, Il 61840
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