1.0 Introduction

The Model 281 is an optically coupled, RS-422 isolation module. The two ports are completely electrically isolated from each other. The Model 281 provides two full duplex, isolated, signal paths, on for data and the other for control signals of the users choice. Power to operate the Model 281 is obtained from the RS-422 driver connected to each port.

2.0 Specifications

Interface: RS-422(note 1)

Data Rate: 0 to 19,200 kilobaud

Power: From RS-422 drivers (note 2)

Connectors: DCE side is DB-25 male, DTE side is DB-25 female

Isolation: 500 Volts AC

Size: 2.25"W x 6.75"L x 1"H

Environment: 0° to 50° C, 5 to 95% RH (no condensation)

Max Transmission Line Length: On both interfaces simultaneously, 26 ga. - 500 feet (each side).

note 1: The model 281 drivers have a minimum differential output of .5 Volts across 100 Ohms. This does not meet the EIA Rs-422 driver minimum output Voltage specification. However it does surpass the .2 Volt maximum receiver input offset, enabling the Model 281 to drive a minimum of 500 feet of wire.

note 2: The Model 281 is powered by one or more of the RS-422 drivers connected to both sides of it. The 281 will draw 20 milliamps maximum from a driver at 2 volts. With a 5 volt source the model 281 will conduct 100ma. This will not harm the 281, but if the customer wishes to pull up an input, use of a 150 Ohm resistor will limit the current to less then 20 ma.

DCE CONNECTOR MALE PIN NUMBER	DIRECTION	DTE CONNECTOR FEMALE PIN NUMBER
2/14		2/14
3/16		3/16
4/19*		4/19*
Or		Or
20/23		20/23
5/13*		5/13*
Or		Or
8/10		8/10
1	NO THROUGH CONNECTION	1
And/Or		And/Or
7		7

* This is the default position, for the strap selectable pins, when shipped from the factory. This is the selection for the RTS/CTS, handshake pins.

The other handshake selection is for the DTR/DCD pins.

One ground connection is required on each side of the Model 281.

3.0 Installation

The control channel (handshake) pins are strap selectable (see table 1 and figure 2). If the factory settings are correct for your application (RTS/CTS, or no handshake modes) connect the model 281 to the equipment to be isolated. The Model 281 is now ready to operate.

If the strap settings need to be changed to the DTR/DCD pins, disconnect the Model 281 from any equipment. Remove the 4 screws on the top cover. Pull off the top cover and move the required straps (see Figure 3). Place the top cover back onto the unit and reinstall the 4 screws. Connect the Model 281 to the equipment to be isolated. The installation process is complete.

4.0 Help

Assistance can be obtained by visiting our Technical Support Center.

Warranty

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. These deliveries will be sent COD freight and 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 number (RMA) is necessary. Assistance can be obtained by visiting our Technical Support Center.
  
Document No. 0315-0135/Rev. A