Models 373 - 10BaseT to Fiber Optic Full Duplex Converter


Reference Manual

Table of Contents

1.0 Introduction
2.0 Installation
3.0 Operation
4.0 Specification
5.0 Help

1.0 Introduction

1.1 Overview

The Model 373/374 Media Translator provides users with an inexpensive means to break the distance barrier of 10BASE-T compliant Local Area Networks while utilizing network connections which are safe from electrical interference. The Model 373 will perform the translation of signals between a 10BASE-T compliant link and a 10BASE-FL compliant link, which allows a user to convert from a twisted-pair segment to a fiber optic segment. The Model 374 performs the same as the Model 373 but has been designed to work on single mode fiber. This will enable users with 10BASE-T terminal equipment to connect via fiber optic link segments which can be extended to a distance of 14 kilometers, or 46,000 feet. Thus a LAN can be extended to distant buildings without the usual concern for electrical interference from other equipment, ground loops, power surges, or nearby lightning strikes. If the connection from server to workstation is a fiber optic segment, it will be impervious to these disturbances.

The twisted-pair-to-fiber media translator allows any network devices with 10BASE-T compliant ports (DTE's, repeaters, fan-out units, hubs) to be connected by fiber optic cable. The media translator converts between electrical signals and optical signals, while assuring that collision information is preserved and translated from one segment to the other. The operation of the device is transparent to the network. Because each port is compliant with its respective section of the IEEE 802.3 specification, full-length segment connections are allowed on both sides of the device.

Five LEDs are used to monitor the status of the device and the connected segments. In addition, a switch is provided which enables or disables the twisted-pair link integrity test.

1.2 Features

  • Translates signal activity between twisted-pair and fiber, including collision information
  • Five diagnostic LEDs provide information regarding device operation and network status
  • Compatible with IEEE 802.3 specifications for 10BASE-T and 10BASE-FL
  • Supports full-length network segments on both ports
  • Switch controllable twisted-pair link integrity test
  • Automatic polarity correction on twisted-pair link
  • Easy to install and operate

1.3 The Model 373/374 Media Translator vs. the Two-Port Repeater

A two-port repeater enables a user to extend the distance of a network. Degenerative effects such as jitter, cable attenuation, and media distortion limit the distance of a link segment. To transmit data across distances longer than this maximum segment length, a repeater is needed to resynchronize and regenerate the data and thus remove the cumulative effects of jitter, cable attenuation, and media distortion. A two-port repeater also enables a user to translate information from one type of media to another. Selection of the appropriate MAUs for the repeater set enables translation from any type of IEEE 802.3 compatible link segment to any other. Data and collision information are preserved and translated across the repeater.

However, if a user simply wants to do media translation, but does not care about extending the distance of the network, a repeater may not be necessary. By removing the signal retiming, preamble regeneration, fragment extension, and auto-partitioning functions of a repeater, the Model 373/374 is able to provide a cost-effective method of translating from one type of media to another.

This does not mean that the user can not take advantage of the additional network distance offered by repeaters. Because the two ports on the media translator are compatible with their associated specifications, the user can connect full-length segments to both sides of the media translator, but must do so knowing that the effects of jitter will not be eliminated by signal resynchronization, and that adding the translator and another segment will add to the total round trip delay for the network.

2.0 Installation

2.1 Location

The Model 373/374 should be located close enough to an AC power source to permit the use of the supplied power module. In addition, it should be placed in an area that is well ventilated and away from electrically noisy equipment. Unshielded twisted-pair connection should be routed such that the effects of interference from other power or data connections are minimized.

2.2 Connections

2.2.1 Power

The power module supplied with the Model 373/374 provides 12 Volts DC at 500 mA maximum to the device through the power connector located next to the RJ-45 connector. The module plugs into a standard 115V, 60 Hz AC power source. An optional 220 Volt, 50 Hz power module is available. There is no ON/OFF switch on the device. When the power is connected to the device, the device is ON. This will be indicated by the power LED being illuminated.

2.2.2 Fiber Optic Segment

The Model 373/374 provides two ST-Type connectors to interface to the fiber optic link. Power should be connected before attaching the fiber optic cables. The fiber optic cables must be terminated with ST-type connectors in order to interface with this device. It is important when dealing with fiber optic cables to assure that the TX on one end of the link is connected to the RX at the other end of the link. Some duplex fiber optic cables are coded to help monitor the direction of data travel. If the fibers are not coded, special attention must be paid to insure a proper connection.

The maximum length of a fiber optic segment is 2 km (6,600 ft) for the Model 373 and 14km (46,000 ft) for the Model 374.

2.2.3 Twisted-pair Segment

The Model 373/374 provides an RJ-45 connector to interface to the twisted-pair link. It is important to note that THE MODEL 373/374 DOES NOT HAVE AN INTERNAL CROSSOVER. This means that on the Model 373/374, pins 1 and 2 are outputs, and pins 3 and 6 are inputs. Thus, if connecting to a DTE, a crossover cable will probably be necessary. However, if connecting to a hub, a straight through cable will probably be necessary, since most hubs have an internal crossover. The user should check the cable specifications for the device to be attached to the other end of the twisted-pair link to ensure proper operation.

The maximum length of a twisted-pair segment is 100 m (330 ft).

3.0 Operation

3.1 Status LEDs

Power - This LED will be illuminated to indicate that external power is connected and the internal power converter is functioning properly and supplying power to the internal circuitry.

Fiber Link Monitor - This LED will be illuminated when the input power at the RX port exceeds a certain minimum level, and there are transitions that indicate either an idle signal or active data. If the power falls below the minimum, or transitions cease, the LED will go off indicating that there is no valid link to the RX fiber port.

Twisted-pair Link Monitor - When link integrity testing is enabled, this LED will be illuminated when the Model 373/374 is receiving proper link pulses from the device attached to the other end of the twisted-pair segment. This indicates that the link is connected and operational. When link integrity testing is disabled, this LED will always be lit when the power is on.

Traffic - This LED will be illuminated to indicate that the data is present at the transmit and receive port of either segment. This indicator is extended with an internal timer for visibility.

3.2 Link Integrity Test Enable/Disable

The Link Integrity enables the user to enable or disable the twisted-pair link integrity test. When the test is enabled (ON), the media translator will transmit link pulses over the twisted-pair segment to the attached network device when transmit data is idle. In addition, when the test is enabled, the media converter will assure that link pulses are being received from the attached network device when receive data is idle. If proper pulses are not being received, the media converter will go into a link fail state and cease operation. During the link fail state, the twisted-pair link monitor LED will be turned off. The link integrity test enables the media converter to ensure that the twisted-pair link is functional.

When link integrity testing is disabled (OFF), the media translator will not transmit link pulses, nor will it monitor incoming link pulses. The twisted-pair link monitor LED will always be lit.

Not all network devices support link integrity testing. The user should check the attached network device to determine if link testing is supported. If the attached network device supports link integrity testing, the testing must be enabled (ON) in the media translator to prevent the network device from interpreting the absence of link pulses as a link failure. Devices compatible with the 10BASE-T standard support link integrity testing.

3.3 Starting Up the Model 373/374

Plug the power adapter into the wall outlet, then attach the power connector to the media converter to turn the device on. Connect the twisted-pair cable and fiber optic cables as described earlier. Set the Link Integrity Test switch to the desired setting. Check the status LEDs for proper device operation.

When the device is operating, input signals to the twisted-pair port are detected, translated into signals compatible with a 10BASE-FL fiber optic link, and outputted to the TX fiber port. Signals inputted to the RX fiber optic port are detected, translated into signals compatible with a 10BASE-T link, and output to the twisted-pair port.

3.4 Diagnostic Checks

3.4.1 Power Connection

When the power connector is inserted into the receptacle in the Model 373/374, the power LED should be lit. If it is not, check to see that the power module is supplying 12 VDC at 500 mA minimum.

3.4.2 Fiber Connection

When the fiber optic link is connected properly, the fiber link monitor LED should be lit. If it is not, check to see that RX on one end of the link is connected to TX on the other end, and vice versa. Assure that the remote unit is powered. If the link is still not operational, check the continuity of the fiber, and assure that the fiber connectors are clean.

3.4.3 Twisted-Pair Connection

When the twisted-pair link is connected properly, the twisted-pair link monitor LED should be illuminated. If it is not, check to see that the twisted-pair cable is such that the transmit pins (1,2) from the Model 373/374 are connected to the receive circuitry on the remote device, and the receive pins (3,6) are connected to the transmit circuitry on the remote device. In other words, check the specifications of the remote device to determine if a crossover cable is necessary. Assure that the remote unit is turned on. If the remote device does not support link integrity testing, make sure that this option is turned off in the Model 373/374 by setting the Link Test switch to the OFF position.

4.0 Model 373 Device Specifications

Power Requirements:
Max Input Power: 12 V at 500 mA

Power Supply Module:
120 VAC,60Hz
(220 VAC, 50Hz Optional)
Output: 12 VDC at 500 mA

Twisted-Pair Interface:
Connector: RJ-45 8-pin jack
Input Impedance: 100 Ohms
Output Level: 2.3 V - 2.7 V
Min. Input Level: 525 mV
Max Link Length: 100 m
Compatibility: IEEE 802.3 Specification for l0BASE-T

Fiber Optic Interface:
Connectors: 2 ST-Style fiber optic connector (AMP 2.5 mm bayonet connector or similar)

Model 373
Max Link Length: 2 km
Fiber Type: multimode 50/125,62.5/125, or 100/140 micron

Peak Transmit Power:
50/125 um: -19.8 dBm minimum
62.5/125 um: -16.0 dBm minimum
100/140 um: -10.5 dBm minimum (measured out of 1 m of cable)

Opt.Power Budget:
50/125 um: 12.7 dBm
62.5/125 um: 16.5 dBm
100/140 um: 22.0 dBm

Model 374
Max Link Length: 14 km
Fiber Type: singlemode 9/125 micron

Peak Transmit Power:
9/125 um: -27 dBm minimum (measured out of 1 m of cable)

Opt.Power Budget:
9/125 um: 9 dBm

Min.Receive Power: -32.5 dBm average (for BER < 10)
Compatibility: IEEE 802.3 specification for 10BASE-FL
Fiber Optic Link Monitor - Green
Twisted-Pair Link Monitor - Green
Traffic - Yellow (Internal timer extends event for better visibility)
Power - Red
Dimensions: 1.5"W x 4.25"L x 1"H
Weight: 16 oz. (including power supply)
Environment: 0° to 50° C, 5 to 95% RH (no condensation)

5.0 Help

If any assistance is required call METROTEK Customer Service at (727)-547-8307 or (727)-547-0687.
Technical Support E-Mail

Document No. 0315-0269
Rev. -


METROTEK 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. METROTEK's sole obligation under this warranty shall be to furnish parts and labor for the repair or replacement of products found by METROTEK 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. METROTEK factory and will be redelivered by METROTEK freight prepaid, except for non- continental U.S.A. locations. These deliveries will be sent COD freight and import/export charges.


Out of warranty equipment may be returned to the FL 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 and can be obtained by calling customer service department telephone 727-547-8307, or Fax 727-547-0687. Reference RMA number on the outside container.

Product Page Application Note Specifications

For more information, contact:
Phone: (727) 547-8307
Fax: (727) 547-0687


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