Model 31

Port Sharing Device


Reference Manual

0315-0122 Rev. B


Printed 11.22.01

Table of Contents

1.0 General Description

2.0 Specifications
2.1     Interface
2.2     Connectors
2.3     Size
2.4     Power
2.5     Controls
2.6     Indicators
2.7     Environment

3.0 Installation
4.0 Help

1.0 General Description

The Telebyte Model 31 Port Sharing Device changes a single RS-232 port into three RS-232 ports, thereby allowing a modem, printer or computer port to be shared by up to three different devices. The only constraint is that only one of the devices can communicate with the shared port at any given time.

The Model 31 is a passive device that attaches to a modem, printer or computer and allows up to three terminals, monitors or other input devices such as bar code readers, mag-stripe units and specialized keypads to be interconnected. The design is based on the concept that only one input port can generate data at any given time.

Semiconductor circuits are utilized to provide isolation of the prime signals in the RS-232 interface. Each port has a DTE/DCE switch associated with it for reversing pins 2 and 3 of its respective RS-232 connector.

The signals that are isolated include the selected Transmit Data Line as well as pins 4 and 20. Each slave port has a DB25 female connector. The main port consists of a DB25 male connector. The simplicity of the device allows for quick and simple plug-in operation.

2.0 Specifications

2.1 Interface

RS-232: Lines supported are 1, 2, 3, 4, 5, 6, 7, 8 and 20

2.2 Connectors

Main port: DB25 male
Slave ports: DB25 female (three)

2.3 Size

2" W x 4" L x 1" H

2.4 Power


2.5 Controls

DTE/DCE selector switch for each port.

2.6 Indicators

Each port has an LED to simplify the setting of the DTE/DCE switch.

2.7 Environment

0o to 50o degrees C, 5% to 95% relative humidity, non-condensing.


3.0 Installation

Connect only one port at a time to the device that will connect to that port. Switch the DTE/DCE switch to a position that illuminates the LED. Disconnect the device and repeat this procedure for each device that will be connected to the Model 31. Once the switch setting has been established, reconnect all the devices through their respective cables. The Model 31 is now properly configured.

4.0 Help

If you require assistance, please visit our Technical Support Center.



TELEBYTE warrants the equipment to be free from defects in material and workmanship, under normal and proper use and in its unmodified condition, for 12 months, starting on the date it is delivered for use. TELEBYTE's sole obligation under this warranty shall be to furnish parts and labor for the repair or replacement of products found by TELEBYTE to be defective in material or workmanship during the warranty period. Warranty repairs will be performed at the point of manufacture. Equipment approved for return for warranty service shall be returned F.O.B. TELEBYTE factory and will be redelivered by TELEBYTE freight prepaid, except for non-continental U.S.A. locations. Non-continental deliveries will be sent COD freight plus import/export charges.

The above warranty is in lieu of all other warranties, expressed or implied, statutory or otherwise, including any implied warranty of merchantability or fitness for a particular purpose. TELEBYTE shall not be liable for any damages sustained by reseller or any other party arising from or relating to any equipment failure, including, but not limited to consequential damages nor shall TELEBYTE have any liability for delays in replacement or repair of equipment.

Out of warranty equipment may be returned to the Greenlawn, NY customer service facility prepaid as described above. Return shipping charges will be billed to the customer. The repaired unit will have a 90-day warranty. In those cases where "NO TROUBLE" is found, a reduced charge will be billed to cover handling, testing and packaging.

Whether in or out of warranty, a Return Material Authorization (RMA) number is necessary and can be obtained by visiting our Technical Support Center. Reference the RMA number on the outside container.

Document No. 0315-0122/Rev. B


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