Versitron F242x User manual

F242x
T1/E1 Fiber-Optic Modem
Technical Manual
Revision A
© July 2015
VERSITRON, Inc.
83 Albe Drive / Suite C
Newark, DE 19702
www.versitron.com
Safeguarding Communications Since 1958

PROPRIETARY DATA
All data in this manual is proprietary and may not be disclosed,
used or duplicated, for procurement or manufacturing purposes,
without prior written permission by VERSITRON.
VERSITRON LIFETIME WARRANTY
All VERSITRON products are covered by a Lifetime Warranty against defects in materials and workmanship. This coverage
is applicable to the original purchaser and is not transferable.
We repair, or at our option, replace parts/products that, during normal usage and operation, are proven to be defective during
the time you own the products, provided that said products and parts are still manufactured and/or available. Such
repair/replacement is subsequent to receipt of your product at our facility and our diagnostic evaluation and review of the unit.
Advance replacements are not provided as part of the warranty coverage.
This warranty does not cover damage to products caused by misuse, mishandling, power surges, accident, improper installation,
neglect, alteration, improper maintenance, or other causes which are not normal and customary applications of the products
and for which they were not intended. No other warranty is expressed or implied, and VERSITRON is not liable for direct,
indirect, incidental or consequential damages or losses.
In the unlikely event a warranty issue should arise, simply contact us at 302-894-0699 or 1-800-537-2296 or via e-mail to
[email protected]m and obtain a Return Material Authorization (RMA) number. Reference this number on the outside of
the shipping container and return the unit (shipping charges prepaid) to us for diagnostic review and repair/replacement as
determined solely by VERSITRON. We pay the shipping charges to return the repaired unit or a replacement unit to you.

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Table of Contents
1Description of Equipment ................................................................................................................4
1.1 Introduction ...............................................................................................................................................................4
1.2 Description of Equipment..........................................................................................................................................5
1.2.1 Functional Characteristics.................................................................................................................................5
1.2.2 Physical Characteristics ....................................................................................................................................5
1.2.3 Specifications.............................................................................................................................................................7
2Installation......................................................................................................................................... 9
2.1 General ......................................................................................................................................................................9
2.2 Site Selection and Mounting......................................................................................................................................9
2.3 Power Requirements..................................................................................................................................................9
2.4 Switch Settings ..........................................................................................................................................................9
2.5 Output Connections .................................................................................................................................................11
2.6 Loopback ................................................................................................................................................................. 11
2.6.1 Fiber/Copper Loopback .................................................................................................................................. 11
2.6.2 Interface Loopback .........................................................................................................................................12
2.7 Initial Checkout Procedure ......................................................................................................................................12
3Operation......................................................................................................................................... 13
3.1 Introduction .............................................................................................................................................................13
3.2 Status Indicators and Alarm Circuits .......................................................................................................................13
3.3 Operating Controls...................................................................................................................................................13
4Theory of Operation ....................................................................................................................... 14
4.1 Introduction .............................................................................................................................................................14
5Maintenance and Troubleshooting................................................................................................ 15
5.1 Introduction .............................................................................................................................................................15
5.2 Fault Isolation ..........................................................................................................................................................15

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1 Description of Equipment
1.1 Introduction
This manual provides general and detailed information on the installation and operation of
the Model F242x FOM II Series T1/E1 Fiber Optic Modems. Section 1 contains a general
description of the equipment. Section 2 contains installation instructions. Section 3 contains
operating instructions. Section 4 provides the theory of operation. Section 5 contains
maintenance and troubleshooting information. Figure 1 is an overall view of the F242x.
Figure 1: Overall View, F242x Fiber Optic Modem

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Figure 2: Rear Connectors
1.2 Description of Equipment
1.2.1 Functional Characteristics
Model F242x modems are designed to operate as point-to-point converters for copper-to-
fiber T1/E1-standard interface extenders. F242x modems transmit over fiber optic cable up to
2km with multimode 850nm LEDs or up to 20km for single mode 1310nm LEDs. The fiber optic
circuit (two F242x modems connected by fiber cable) has data rates and electrical signal
characteristics that conform to ANSI T1.403, AT&T Pub. TR54016 and TR62411, and
G.703/G.704 standards. Electrical signals on copper cable are converted to fiber optic signals by
the F242x modem, and AMI or B8ZS/HDB3 data protocols are decoded.
1.2.2 Physical Characteristics
F242x modems measure 7.0W x 0.84H x 11.6L in. (17.8 x 21. X 28.9 cm) and are designed
for mounting in a variety of VERSITRON enclosures. Table 1 lists dimensions of enclosures and
chassis. Standalone option is a single card enclosure (HF-1). 19” rack mount options include 2-
slot chassis (HF-2SS), 20-slot chassis (HF-20A) and VERSITRON Versimux II chassis (VMX20).
Each F242x modem installed in an HF-1 or HF-2SS requires a power adapter Model PSAC08
(US) or PSAC09 (European) providing 12 VDC, 1A with a one-pin connector for electrical input
on the back of the card. Note: Other power adapters are available, such as UK and Australian.
Model
Number
Description
F2422
T1/E1 fiber modem, multimode, 850nm LED, LC optics, 1.544Mbps/2.048Mbps,
distances to 2km.
F2425
T1/E1 fiber modem, single mode, 1310nm LED, LC optics,
1.544Mbps/2.048Mbps, distances to 20km.

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There is an 8P8C modular connector (RJ48C standard), and two BNCs for the digital interface and
an LC connector for the fiber optic interface, all on the back of the card. F242x modems installed
in a HF-20A or VMX20 require a Model AC300WR Power Supply / System Monitor. The F242x
Modems have six LED indicators on the front panel: power on (PWR), alarm (ALM), transmit
data present (TXD), receive data present (RXD), bipolar violation (BPV), and loopback mode
indicator (LOOP). No audible alarm is available.
Table 1: Enclosures / Chassis
Model #
(Part #)
Dimensions
Description
Power Supply Required*¹
HF-1
(19052)
7.1" W x 1.3" H x 11.6" L
Single Card Standalone Enclosure
PSAC08 PSAC09
(LTWPD1210PLX) (LTWPD1210EPL)
HF-2SS *²
(19629)
19" W x 1.7" H x 13.8" L
2-Slot Rack Mount Chassis
PSAC08 PSAC09
(LTWPD1210PLX) (LTWPD1210EPL)
HF-20A
(32406)
19" W x 7.1" H x 11.6" L
20-Slot Rack Mount Chassis
AC300WR
(32410)
VMX20
Versimux II
7.0" H x 19.0" W x 11.6" D
(17.8 x 48.0 x 29.5 cm)
20 Card Rack-Mount Chassis
AC300WR
(32410)
*¹ Note: US Model - PSAC08; European Model – PSAC09; Other supplies are available
*² Note: One Power Supply per Modem required.

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1.2.3 Specifications
Protocol: Synchronous
Data Rate: (N x 64 Kbps) 1.544 Mbps / 2.048 Mbps
Operation: Full duplex or simplex.
Optical Interface: LC connectors.
Digital Interface: Signal levels conform to ANSI T1.403, AT&T Pub. TR54016, TR62411, and
G.703/G.704 standards.
Electrical Interface: RJ48C, or BNC.
Dimensions: 7.0" wide x 0.84" high x 11.6" deep (17.8 x 2.1 x 28.9 cm).
Weight: 16.0 oz. (0.45 kg).
Power Requirements: 120 VAC, 1.4 Watts, with optional DC wall transformer (VERSITRON
Model PSAC08, providing 12 VDC, 1 A, US; VERSITRON Model PSAC09, European). Other
DC wall transformers are available.
Environment: 0° to +50°C (32° to +122°F) operating temperature; up to 95% relative humidity
(non-condensing); up to 10,000 feet altitude; storage temperature -40° to +70° C.
Table 2: Optical Performance
Model
F2422
F2425
Wavelength
Multimode 850nm
Single Mode 1310nm
Link Budget
14  1 dB
19  1 dB
Operating Range
2km
20km
Fiber Optic Cable
50/125,62.5/125,100/140
8/125, 9/125,10/125

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Table 3: T1 Compatibility
Format
ESF
(Extended Super Frame)
D4
(Super Frame)
AMI
Yes
Yes
B8ZS
Yes
Yes

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2 Installation
2.1 General
This section contains detailed information on the installation and initial checkout of the
F242x modems. Section 2.2 contains general information on site selection and rack mounting.
Sections 2.3 through 2.6 contain detailed instructions for connecting the modems to your system
and selecting the different options. Section 2.7 contains initial checkout procedures.
2.2 Site Selection and Mounting
F242x modems are designed to connect directly to the serial port (RJ48C, or BNC
Connector) of line or multiplexer equipment with a cable (customer supplied). Mounting options
include standalone single card (HF-1) or 2-slot (HF-2SS) or 20-slot (HF-20A) rack mount chassis.
The F242x modems can also be used with the Versimux II multiplexer platform. In this case, the
units are installed in the 20-slot VMX20 rack-mount chassis.
2.3 Power Requirements
F242x modems operate from an AC power source or a DC power source with a DC voltage
of +12 VDC, 1A. The power supplies used when installed in a HF-1, or HF-2SS are VERSITRON
Model PSAC08 (US), Model PSAC09 (European), or other power supply from VERSITRON
providing 12 VDC, 1A. Connect the power transformer to the F242x unit before inserting its plug
into an AC power source. No special tools are required. DC power may be used instead of an AC
transformer, if available. This requires a 2.5 mm socket with positive on the center and common
on the concentric, and providing +12 VDC at 1A When installed in a HF-20A or VMX20, the
AC300WR Power Supply / System Monitor is used to supply power for all FOM II series circuit
cards installed into the chassis. The AC300WR is a redundant power supply.
2.4 Switch Settings
F242x modems have one 8-position switch and two double throw switches onboard the
circuit card. These switches are shown in Figure 3. The 8-position switch is labeled "S1" on the
circuit card, and is positioned such that the "ON" setting of each of the 8 switch positions is
towards the fiber optic connection. The settings of the 8 switch positions are as specified in
Table 4 and Table 5. Position 1 on the switch is used to set the line type T1 or E1. Position 2 is
used to set the termination impedance for the T1/E1 interface, as shown in Table 4. Position 3 is
used to power down the receiver. Position 4 is used to set the protocol for the data transmitted

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on the T1 link, and may be set for AMI or B8ZS protocols. Position 5 sets the copper cable
length for short haul or long haul operation. These switches must be set properly prior to
operation. Three loopback settings may be changed using switch positions 6 and 7, as shown in
Table 5. The fiber loopback is controlled from the front panel of the F242x while in operation.
The other two switches S3 and S4 are used to enable the BNC connections. In the “ON”
position the BNC connectors J6 and J7 are enabled. Note the switches are mounted so the slide
is moved in the direction of the BNC to enable.
Figure 3: F242x Switch and Connector Locations

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Table 4: Switch Settings
SWITCH 1
NAME
“ON”
“OFF”
POSITION 1
T1_E1
E1
T1
POSITION 2
Termination
120 Ohm(E1 Mode)
110 Ohm(T1 Mode) for
Japanese terminations
75 Ohm (E1 Mode)
100 Ohm (T1 Mode)
POSITION 3
Receive Power Down
Receiver Powered Down
Normal Operation
POSITION 4
Encoding
AMI(T1 Mode)
HDB3(E1 Mode)
B8ZS(T1 Mode)
POSITION 5
Copper Cable Length
Long Haul
Long Cable Lengths
>255ft
Short Haul
Short Cable Lengths
< 255ft
POSITION 6
Loop1
See Table 5.
POSITION 7
Loop2
POSITION 8
Do Not Use
Factory Setting “OFF”
Factory Setting “OFF”
Switch 3
Input
BNC (J7) enabled
RJ48C pins 1 and 2
enabled
Switch 4
Output
BNC (J6) enabled
RJ48C pins 4 and 5
enabled
Important: Set all switches prior to operation of the unit.
Table 5: Switch Settings for Loop Modes
POSITION 6
POSITION 7
APPLICATION
OFF
OFF
No Loop
ON
OFF
Analog Loop
OFF
ON
Digital Loop
ON
ON
Remote Loop
2.5 Output Connections
F242x modems use a standard RJ48C, or two BNC (for 75 Ohm E1) connectors for the
electrical signal interface. Only four of the pins are used, however. Receive data is input on Pins
1 and 2 and transmit data is output on Pins 4 and 5.
2.6 Loopback
F242x modems have two loopback features. The first Loopback feature allows the user to
test the fiber optic circuitry of the local unit, and the copper circuitry of the local unit. The second
loopback feature loops the interface circuitry back to the remote F242x (analog and digital loop),
and back to the local network (T1/E1) equipment (remote loop).
2.6.1 Fiber/Copper Loopback

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The fiber optic inputs and outputs of the F242x modems are connected to a multiplexer.
When the front panel loopback switch (LB) is switched ON, the multiplexer control bit is set high
and fiber optic input data is looped to the output and back to the source. The copper signals
entering through the interface circuitry are encoded and decoded by the multiplexer and likewise
looped back to their source. If both the fiber and copper input and output signals match, then the
optical and interface circuitry of both units is operating properly.
2.6.2 Interface Loopback
As listed in Table 5, switch positions 6 and 7, are used to loop the data signals at the interface.
This allows for testing within the T1/E1 interface circuitry. Analog Loop causes the interface to
loop at the tip and ring back through the fiber optic interface towards the remote device. Digital
Loop occurs after the decoders, but before the analog drivers, in the T1/E1 interface circuit.
Remote Loop causes the T1/E1 interface to loop to the connected T1/E1 equipment.
2.7 Initial Checkout Procedure
F242x modems contain no power on/off switch. Once the unit is properly installed and
power is applied it is considered fully operational. The power indicator (PWR) should remain on
as long as power is supplied to the unit. Upon initial power up, with no signal connections made,
the PWR, alarm (ALM) and bipolar violation (BPV) LED indicators should be on. When signal
connections are properly made, the transmit data (TXD) and receive data (RXD) LED indicators
should be on and the ALM LED should go off. The BPV LED can be cleared by pressing the RST
button.
Before beginning system operation the following items should be checked to verify proper
installation:
1. Verify that the power plug is seated fully into the F242x or seated firmly in the rack mount
enclosure.
2. Verify that the fiber optic cable is firmly seated in the LC connector.
3. Verify that the ALM LED goes out when the signals are applied to the F242x.
4. Verify that the LOOP LED comes on and goes out with the LB switch on the front panel.
5. Verify the switch settings are correct for the circuit configuration.
If a malfunction is detected during the initial checkout procedure, refer to section 5 for
information on isolating the malfunction in the unit.

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3 Operation
3.1 Introduction
This chapter contains a description of the operating controls and indicators associated
with the F242x modems. Since the modem is designed for continuous and uninterrupted
operation, there are no operating requirements. Once powered up, it should remain in service as
long as required.
3.2 Status Indicators and Alarm Circuits
There are six LED indicators on the F242x: power (PWR), alarm (ALM), transmit data
(TXD), receive data (RXD), bipolar violation (BPV), and loopback (LOOP). No audible alarm
is available. The ALM LED is activated when no signal is present at the fiber optic interface.
When AMI signals are decoded, bipolar violation circuitry checks the signal. The BPV LED is
activated when a violation is detected and remains on until turned off by the RESET switch on
the front panel.
3.3 Operating Controls
The only operating controls associated with the F242x modems are two front panel
switches. The LB switch is used to enable the loopback capability of the circuit. This is
described in Section 2.6 and is normally only used for diagnostic purposes when initializing or
reconfiguring the system using the F242x. The reset push-button switch is only used if a bipolar
violation occurs. The switch settings onboard the circuit card are described in Table 4 and Table
5 in Section 2.4 and are set prior to first using the modem. Further changes are not required
unless the system requirements change.

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4 Theory of Operation
4.1 Introduction
F242x modems provide a transparent, synchronous path for T1-standard or E1-standard
signals. By converting to fiber optic signaling, a distance of 2km for 850nm multimode LEDs or
20km for 1300nm single mode LEDs may be traversed without the need for a repeater or amplifier.
In addition, the use of fiber optic cable as the transmission medium provides EMI/RFI protection
and data security.
In the F242x transmitter circuitry, the data is received via Pins 1 and 2 of the RJ48C
connector or BNC(J7) for E1 75 Ohm. The signal is decoded for AMI or B8ZS protocol for T1,
or AMI or HDB3 protocol for E1. The signal is then Manchester encoded (which embeds a clock
signal) with a Field Programmable Gate Array (FPGA). Next the signal is converted into an optical
signal. The optical signal transmitter then sends the signal out onto the fiber optic cable.
Through the receiver circuitry of the F242x the same process occurs in reverse. First the
optical signal is received and converted back to an electrical signal. The FPGA decodes the
Manchester data and clock signals. The data signal is then encoded for the AMI or B8ZS/HDB3
protocol. The encoded output is sent to Pins 4 and 5 of the RJ48C or BNC(J6) for E1 75 Ohm.
The transmission through the units is transparent to the end equipment.

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5 Maintenance and Troubleshooting
5.1 Introduction
This chapter contains general information designed to isolate a malfunction in the F242x
modems to a replaceable unit. These units are not equipped with redundancy. Therefore, a failure
in one of these units would interrupt service.
5.2 Fault Isolation
The steps in Table 6 should be taken to check a non-operating modem. Contact
VERSITRON Customer Service for additional diagnostic assistance or to arrange for repair as
necessary.

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Table 6: Non-Operational Indicators
STATUS INDICATOR
PROBABLE CAUSE
CORRECTIVE ACTION
POWER (PWR) LED is off.
No AC power.
Check that both ends of the
Transformer are connected.
Tripped PTC.
Unplug the device for a few minutes to
allow the PTC to cool, then try again.
Other power supply circuit problem.
Contact VERSITRON Customer
Service for assistance.
ALARM (ALM) LED is on.
Incorrect optical signal level received
at receiver input.
1. Check that fiber optic cable is
properly connected.
2. Check that the remote unit
power is on and the fiber is
connected.
3. Measure the optical levels on
both ends (if possible) in order
to check the optical link.
4. Contact VERSITRON
Customer Service for
assistance.
DATA (TXD, RXD) LEDs are off
or not responding as expected.
Switches in wrong position.
1. Check that the switch is set for
the correct electrical interface
protocol.
2. Check that cable length switch
is set for the appropriate cable
length.
No input on the electrical interface
connector.
Check that the interface connector is
connected securely, and the connector
selection switches are set appropriately.
BPV LED continuously on.
Switches in wrong position.
Check that the switch is set for the
correct AMI or B8ZS/HDB3 protocol.
Inverted input on the electrical
interface connector.
Check that the interface connector is
wired correctly.