1.0 General Description

The Model 203, Two-Wire Groundless Short Haul Modem, allows for the full duplex transmission of data over a single twisted pair. This design has a significant technical improvement over previous two-wire, full duplex, DC coupled short haul modems/line drivers. Prior technology was based upon establishing ground link between units using one of the wire comprising the single twisted pair. Subsequently, any AC noise or perturbations which were reflected on the grounds of either system at the ends of the link had the ability to degrade the data. The Model 203 does not employ this technology but instead uses a fully differential, simultaneous, drive/receive technique on a single pair.

2.0 Specifications

2.1 Interface:
Conforms to EIA RS-232 and CCITT V.24. Pin 2 and 3, Transmit and Receive Data; Pin 4, Request to Send, connected to Pin 5, Clear to Send; Pin 6, Data Set Ready, Pin 8, Data Carrier Detect, and Pin 20, Data Terminal Ready, connected together; Pin 7, Signal Ground.

2.2 Connections:

2.2.1:

2.3 Transmission: Asynchronous, full duplex on one twisted pair.

2.4 Operating Distance:
The following table gives maximum distance as a function of data rate and wire size:

2.5 Power: None required, all power derived from RS-232 interface.

2.6 MTBF: 373,000 Hours (per MIL-STD-HDBK-2170)

2.7 Size: 2"W x 2.75"L x .75"H

2.8 Environment: 0° to 50° C, up to 95% humidity non-condensing

3.0 Installation

3.1 Digital Interface
The digital interface for the Model 203 is a DB-25 connector. The Model 203 can be ordered with a male DB-25, 203M or a female DB-25, 203F.

3.2 Analog Interface
The fiber interface is an ST connector.

3.2.1 Screw Terminals and Modular RJ-11

3.2.2 Screw Terminals

The Model 203 comes equipped with two screw terminals labeled + and -.

4.0 Operation

The only user control is the DTE/DCE switch located on the top of the unit. When the switch is in the DTE position the unit is set to connect to a DCE device, such as a dial-up modem. When the 203 is configured for DCE the 203 is to be used with a DTE device, i.e., a terminal or PC.

When connecting the 203 to each other one twisted pair of wire is used and the + on one unit should go to the + on the other unit and - to the -.

5.0 Connector Pin Assignments

* Connected together
** These signals may be reversed using the selector switch
*** Connected together
**** Connected together

6.0 Power

The Model 203 will derive all power from the data input pin (must be -5.5V with the Model 203 connected and in a quiescent state.)

7.0 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. 0315-0091/Rev. B