JPS QMT-1B User manual

Installation and Operation Manual
QMT-1B
IP Backhaul Remote
For
The SNV-12 Voter
JPS Interoperability Solutions
5800 Departure Drive
Raleigh, NC 27616
919-790-1011
Email: [e-mail] / [e-mail]
www.jpsinterop.com
JPS P/N 5200-300200 Revision 1.0 August 2020

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NOTICE
© 2020 JPS Interoperability Solutions. SNV-12, QMT-1B, SVM-2 and SVM-3
are all trademarks of JPS Interoperability Solutions, Inc.
JPS Interoperability Solutions reserves the right to make changes to the
equipment and specifications without prior notice.
CAUTION
Changes and modifications to this equipment not expressly approved by JPS
Interoperability Solutions could impair proper operation of the equipment
and/or could void user’s warranty.
JPS Interoperability Solutions
[phone]
[email protected]
[e-mail]
5800 Departure Drive
Raleigh, NC 27616

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Table of Contents
1GENERAL INFORMATION........................................................................................................................1-1
1.1 SCOPE.....................................................................................................................................................1-1
1.2 OVERVIEW .............................................................................................................................................1-1
1.3 SYSTEM REQUIREMENTS........................................................................................................................1-3
1.4 GENERAL NOTES....................................................................................................................................1-3
1.5 THE QMT-1B RADIO INTERFACE...........................................................................................................1-4
1.6 NETWORK INTERFACE............................................................................................................................1-4
1.7 SPECIFICATIONS.....................................................................................................................................1-5
1.8 EQUIPMENT AND ACCESSORIES SUPPLIED .............................................................................................1-6
1.9 DIFFERENCES BETWEEN THE QMT-1B AND THE QMT-1.......................................................................1-6
2INSTALLATION ...........................................................................................................................................2-1
2.1 GENERAL ...............................................................................................................................................2-1
2.2 UNPACKING AND INSPECTION................................................................................................................2-1
2.3 RESHIPMENT OF EQUIPMENT..................................................................................................................2-1
2.4 INSTALLATION OVERVIEW.....................................................................................................................2-2
2.5 INSTALLATION CONSIDERATIONS ..........................................................................................................2-3
2.5.1 Power Requirements.........................................................................................................................2-4
2.6 INSTALLATION CHECKLIST ....................................................................................................................2-4
2.7 REAR PANEL CONNECTORS....................................................................................................................2-4
2.7.1 DC Input Connector .........................................................................................................................2-4
2.7.2 Audio Level Adjustment....................................................................................................................2-4
2.7.3 Connection to Radio.........................................................................................................................2-4
2.7.4 Network Connection.........................................................................................................................2-6
2.7.5 RS-232 ..............................................................................................................................................2-6
2.7.6 Internal Jumper Configuration.........................................................................................................2-7
3CONFIGURATION.......................................................................................................................................3-1
3.1 GENERAL ...............................................................................................................................................3-1
3.2 QMT-1B CONFIGURATION SELECTIONS................................................................................................3-2
3.2.1 QMT-1B Name: ................................................................................................................................3-2
3.2.2 IP Address:.......................................................................................................................................3-2
3.2.3 Subnet Mask:....................................................................................................................................3-2
3.2.4 Gateway:...........................................................................................................................................3-3
3.2.5 QMT-1B RoIP Port: .........................................................................................................................3-3
3.2.6 QMT-1B Sync Port:..........................................................................................................................3-3
3.2.7 SVM-3 IP:.........................................................................................................................................3-3
3.2.8 SVM-3 RoIP Port: ............................................................................................................................3-3
3.2.9 SVM-3 Sync Port:.............................................................................................................................3-3
3.2.10 Squelch Type: ...................................................................................................................................3-3
3.2.11 COR Hangtime:................................................................................................................................3-3
3.2.12 COR Inhibit ......................................................................................................................................3-4
3.2.13 RX Input Level..................................................................................................................................3-4
3.2.14 Duplex:.............................................................................................................................................3-4
3.2.15 TX Output Level................................................................................................................................3-4
3.2.16 TX Delay:..........................................................................................................................................3-4
3.2.17 Restoring Factory Defaults ..............................................................................................................3-4
3.2.18 Store Setup Changes with SAVE Command.....................................................................................3-5
3.3 QMT-1B ACTIVITY LOG........................................................................................................................3-5
3.4 QMT-1B SECURITY...............................................................................................................................3-6
3.5 UPDATING THE QMT-1B SOFTWARE.....................................................................................................3-7

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4OPERATION ................................................................................................................................................. 4-1
4.1 GENERAL............................................................................................................................................... 4-1
4.2 OPERATION AT POWER-UP.................................................................................................................... 4-1
4.3 POWER LED .......................................................................................................................................... 4-1
4.4 LINK ACTIVE LED................................................................................................................................. 4-1
4.5 CHANNEL ACTIVE LED......................................................................................................................... 4-1
4.6 AUDIO INPUT LED ................................................................................................................................ 4-1
5QMT-1B TROUBLESHOOTING................................................................................................................ 5-1
6QMT-1B FAQ (FREQUENTLY ASKED QUESTIONS).......................................................................... 6-1
6.1 GENERAL............................................................................................................................................... 6-1

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List of Figures
FIGURE 1-1 SNV-12 VOTING SYSTEM WITH SVM-3 SITE VOTER MODULES AND QMT-1B REMOTES....................1-2
FIGURE 1-2 QMT-1B BASIC BLOCK DIAGRAM.........................................................................................................1-4
FIGURE 2-1 FRONT &REAR PANEL VIEWS...............................................................................................................2-3
FIGURE 3-1 QMT-1B INFORMATION PAGE ..............................................................................................................3-1
FIGURE 3-2 CONFIGURATION PAGE..........................................................................................................................3-2
FIGURE 3-3ACTIVITY LOG PAGE...............................................................................................................................3-5
FIGURE 3-4 SECURITY PAGE.....................................................................................................................................3-6
FIGURE 3-5 SOFTWARE UPDATE PAGE.....................................................................................................................3-7
List of Tables
TABLE 1-1 SPECIFICATIONS ................................................................................................................................1-5
TABLE 1-2 EQUIPMENT AND ACCESSORIES SUPPLIED.........................................................................................1-6
TABLE 2-1 BASIC INSTALLATION CHECKLIST.....................................................................................................2-4
TABLE 5-1 TROUBLESHOOTING TABLE...............................................................................................................5-1

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Glossary
Glossary
COR
Carrier Operated Relay
A signal from a receiver that gives a positive indication
that a carrier or signal is being received and that the
receiver is unsquelched. It has the same function as
Carrier Operated Squelch (COS).
COS
Carrier Operated
Squelch
See COR.
DHCP
Dynamic Host
Configuration Protocol
A method of automatically assigning an IP address to an
Ethernet device at startup time. This method conserves
IP addresses in networks where devices do not stay
connected permanently.
DSP
Digital Signal Processor
A type of microprocessor, which is optimized for signal
processing functions.
Idle Tone
Tones that are inserted into the audio stream when a
radio is squelched. Their absence indicates a receiver
unsquelched condition. Also called Pilot Tones.
IP
Internet Protocol
A protocol designed to allow communications between
computers on different networks.
LAN
Local Area Network
A group of computers and associated devices that share a
common communications line, typically within a small
geographic area.
NAT
Network Address
Translation
A scheme where multiple units can share one IP address,
usually behind a router.
Pilot Tone
See Idle Tone.
PTT
Push-to-talk
A signal to a radio transmitter, which controls the actual
transmission of radio frequency energy over the air. Also
called a keyline.
RoIP
Radio Over IP
A method of converting analog radio audio and flow
control signals into data and sending it to a distant unit to
be re-converted back into analog audio.
TCP
Transmission Control
Protocol
An additional layer to the Internet Protocol, which
ensures delivery of packets, sent across the network. It
can handle situations such as lost packets or packets
arriving out of order.
UDP
User Datagram Protocol
An additional layer to the Internet Protocol which does
not ensure delivery of packets, but which offers much
lower transmission overhead than TCP.
VoIP
Voice over Internet
Protocol
Also called Voice over Packet (VoP), a method of
sending voice communications across a digital network.
WAN
Wide Area Network
A network, which is spread out over a wider area, such
as around a city or state. It may include other public or
shared networks.

1General Information
1.1 Scope
This instruction manual provides the information necessary to install and operate the QMT-1B
IP Backhaul Remote. This manual assumes a basic understanding of the SNV-12 voter, analog
voter fundamentals, and the SVM-3 site voter module. See also the manual for the SNV-12 and
any manual addenda relative to the SVM-3 module.
1.2 Overview
The SNV-12 Voter has long been the leader in analog receiver voting. Prior to the introduction
of IP backhaul made possible by the QMT-1B working in concert with the SVM-3 modules, all
audio input into the SNV-12 was strictly synchronous, interfaced to SVM-2 modules. The
QMT-1B/SVM-3 pair allow voting receiver audio to be transported via non-synchronous IP.
To gain a good understanding of the system, it’s worth considering some of the technical
roadblocks that had to be overcome to make it work:
•An analog voter can function properly only if audio from all unsquelched voting
receivers is time-synchronized when it reaches the voter. Unfortunately for this
function, IP data transfer is not concerned with timing.
•Synchronization is needed because analog voters chose the best site by comparing FM
noise levels within a standard audio spectrum –at the same frequencies that carry
speech. High frequencies within the speech content alter the noise measurement, but all
balances out if audio is synchronized.
•Also, the voter may need to be able to switch to a new voted site during a field
transmission, and it must be able to do so without the listener experiencing any echoes
or missed syllables as the voter transitions from one site to another.
•Most codecs do a poor job of accurately transferring FM noise, simply because they are
not optimized to do so. This means that an SNV-12 module would not be able to do as
accurate a measurement on digitized RX audio as it does on analog RX audio
The SVM-3/QMT-1B pair resolves these potential problems:
The QMT-1B digitizes the audio for transport to the SVM-3 module, but also performs a pair
of other functions –it performs a Signal Quality (FM Noise) measurement on the analog audio
before digitization and also adds a time stamp.
This information is sent as metadata along with the digital audio packets. The SVM-3, in
concert with the SNV-12 voter, returns the audio to analog, uses the timestamp to
resynchronize the audio, and compares Signal Quality measurements to determine (and vote)
the best site.

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Figure 1-1 SNV-12 Voting System with SVM-3 Site Voter Modules and QMT-1B Remotes
QMT-1B remotes reside at the receiver site, one QMT-1B per receiver. By being placed at the
receiver, the QMT-1B can accurately measure the Signal Quality before the audio is encoded
into RoIP. The QMT-1B has an analog interface with the receiver/transceiver and can detect an
unsquelch condition by either a hardware COR line or by absence of an Idle Tone (sometimes
called a Pilot Tone). When the QMT-1B detects an Unsquelch condition, it begins taking
signal quality measurements of the receiver audio, adds time stamps, and encodes the audio
before sending the audio and metadata in a JPS-proprietary format.
The SVM-3 modules reside in the SNV-12 chassis. Each SVM-3 can connect to as many as
three QMT-1B remote units. The SNV-12 voter chassis can accommodate up to 12 SVM-3
modules providing a total of 36 receiver streams to the chassis.
SVM-3 modules can also coexist with SVM-2 modules in the same chassis, with some sites
passing analog RX audio to the voter, and others sending digitized audio via a QMT-1B.
When SVM-3 modules are added to an existing SNV-12 voter chassis, no changes are required
other than updating the CPM-3 Module to the latest firmware and then configuring the new
hardware. The CPM-1 Module cannot be used in a chassis equipped with SVM-3 modules.

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1.3 System Requirements
The IP network used with the SVM-3 modules must meet certain minimum requirements.
While the voter system may continue to work if some of these parameters are not met, the
overall system performance may be degraded.
For example, in order to time-synchronize audio signals, the quicker-to-arrive signals must be
delayed until the slowest one arrives. If the time variation is too long, normal communications
may be difficult to maintain.
For these reasons, the SVM-3 IP Backhaul is not intended to be run on public networks (i.e. the
Internet) because of widely varying performance. Note that public networks can be
overwhelmed during the types of incidents when proper performance is most vital.
The network that the SVM-3/QMT pair is used on must to meet the following specifications:
•100 Kbits/per second throughput per QMT-1B audio channel in each direction. 200
Kbps for a duplex channel.
•Packet loss less than 0.1%.
•Differential latency between RX sites less than 10ms.
•Jitter less than 5ms.
1.4 General Notes
Compatibility with Simulcast Systems
Outgoing QMT-1B audio CANNOT transport outgoing simulcast audio precisely or be
consistently timed to support simulcast transmissions. It is suitable for single transmit site
operation, TX steering, and multisite (different frequencies at different sites).
Site Totals
•An SNV-12 system with IP backhaul can consist of a single chassis, with up to 12
SVM-2 or SVM-3 modules. A larger system uses a Master Chassis that is connected to
and controls one or two Expansion Chassis for a total of 36 plug-in modules.
•Each SVM-2 module can serve only one remote voting site, connected by traditional
analog methods.
•Each SVM-3 module can serve up to three remote voting receiver sites and always
counts as three sites towards the maximum system site total of 60 (even if an SVM-3 is
interfaced to fewer than three receivers).
The main point to remember is that any combination of SVM-2 and SVM-3 modules can be
used in an Expanded system however the total site count cannot exceed 60 sites.

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1.5 The QMT-1B Radio interface
The QMT-1B employs the radio interface designed and optimized by JPS Interoperability
Solutions and therefore:
•Includes the radio interface DSP algorithms relevant to the IP Voting Backhaul
application.
•Can use any of the large number of custom interface cables, designed and optimized by
JPS Systems Engineering, covering over 300 different radio makes and models.
See Section 2.7.3 for complete information on the radio interface.
1.6 Network Interface
The QMT-1B is a 10/100BASE-T Ethernet device and each unit has a unique Ethernet address
and an RJ-45 physical interface jack. A 10/100BASE-T device operates at either 10 or 100
Mbps and interconnects to an Ethernet hub or switch using standard CAT 5 twisted pair cable,
also known as UTP. The maximum cable length between a QMT-1B and its hub port is 100
meters. The QMT-1B’s Ethernet port can be linked with virtually any LAN, WAN, or the
Internet, no matter which topology or cabling system is in use.
Figure 1-2 QMT-1B Basic Block Diagram

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1.7 Specifications
Table 1-1 Specifications
RX Audio Input
Input impedance
600 ohms balanced transformer coupled, 47k ohms selectable.
Input Level
Incoming signals adjustable from –26 to +10 dBm to set -10 dBm nominal
input; +15 dBm clipping.
Frequency Response
10 Hz to 3600 Hz +/- 2dB.
Digitized Audio to SVM-3
uLaw Vocoder, 64 Kbps data rate (with metadata overhead, throughput as high
as 100Kbps per channel)
COR Input
Input impedance
47k ohm pull-up to +5V.
Polarity
COR: Selectable active low or active high;
Threshold
+2.5V nominal.
Protection
Up To + 100 VDC.
Note: Above for Hardwired COR Output signal from receiver. Idle Tone COR also available; 1950 or 2175 Hz.
TX Audio Output
Output Impedance
Balanced 600 Ohms, Transformer Coupled
Output Level
Adjustable from –26 to +10 dBm, -10 dBm nominal factory default; +15 dBm
clipping into a 600-ohm load.
Network & Device Throughput
Timing Variability
+/- 100 microseconds (not suitable for Simulcast transmissions)
Frequency Response
10 Hz to 3350 Hz +/- 2dBm.
Distortion
Typically, < 1%
PTT Output
Output Type
PTT Relay, Open drain selectable.
Maximum Sink Current
100 mA for open drain, 300 mA for PTT relay.
Max Open Circuit Voltage
+60 VDC for open drain, +100 VDC for PTT relay.
Network Interface
Interface Type
10/100BASE-T Ethernet, 10 or 100 Mbps; RJ-45 Connector.
Protocols
TCP; UDP for Audio and Status.
General/Environmental
Programming/Configuration
Web-based
Front Panel
Power, Link Active, Channel Active, and Audio Level LEDs.
Rear Panel
Audio/Data (DB15 Female), Serial, Network, and Power Connectors.
Input Power (12 VDC Nom)
+11 to +15 VDC @ 0.5A max. Wall cube supplied operates on 100-240 VAC.
Power Connector
Coaxial Jack, 2.5 mm ID, 5 to 5.5 mm OD; Center Pin Positive; The DC input
is reverse polarity protected.
Size and Weight
1.36”H x 6.50”W x 6.50”L (3.45 x 16.5 x 16.5 cm). 1.2 lbs. (0.5kg).
Temperature
Operating: -30 to +60 degrees C. Storage: -40 to +85 degrees C.
Humidity
Up to 95% @ 55 degrees C.

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1.8 Equipment and Accessories Supplied
Table 1-2 Equipment and Accessories Supplied
QMT-1B Shipping Level - JPS P/N 5170-200000
Quantity
Item
JPS P/N
1
QMT-1B Final Assembly
5200-300000
1
DC Power Supply [100 to 240 VAC, 47-63 Hz to +12 VDC]
1620-240061
1
Accessory Kit
5200-300150
1.9 Differences between the QMT-1B and the QMT-1
The QMT-1B is a modern redesign of a previous JPS product, the QMT-1, and maintains
compatibility with that unit. Some improvements were made in the new design which
necessitated some differences between the two units. In most cases these differences will be
transparent to the user. The differences are outlined below.
•The pinout of the Audio/Control connector on the rear panel of the unit is different
between the QMT-1 and the QMT-1B. The QMT-1B pinout has been changed to match
that of other JPS products such as the ACU product family. This allows standard JPS
radio cables to be used with the QMT-1B with no adapter needed. Previously an audio
crossover adapter was included with the QMT-1 to allow standard JPS radio cables to
be used. This adapter is not required with the QMT-1B and is not included. Please refer
to the pinout of the Audio/Control connector.
•The QMT-1B uses transformer-coupled balanced audio for both input and output audio.
The QMT-1 only had balanced input audio and single-ended output audio.
•The QMT-1B audio input and output levels are remotely adjustable via the web browser
interface and are saved in non-volatile memory. This allows audio level adjustments
without requiring the operator to be at the location where the QMT-1B is installed. The
QMT-1 had rear panel mechanical potentiometers for the adjustment of audio input and
output levels.
•The QMT-1B uses hardware relay contacts for PTT output while the QMT-1 had a
solid-state (open drain transistor) keying output. There is a jumper selectable solid-state
output available on the QMT-1B as well, but the default is to use the relay for PTT. The
relay allows for higher keying voltages and currents than the solid-state output.
End of Section One

2-1
2Installation
2.1 General
This section provides the instructions for unpacking, inspection, installation and set-up. Also
included are directions for reshipment of damaged parts or equipment.
2.2 Unpacking and Inspection
After unpacking the unit, retain the carton and packing materials until the contents have been
inspected and checked against the packing list. If there is a shortage or any evidence of
damage, do not attempt to use the equipment. Contact the carrier and file a shipment damage
claim. A full report of the damage should also be reported to the JPS Customer Service
Department. The following information should be included in the report:
Order Number
Equipment Model and Serial Numbers
Shipping Agency
Date(s) of Shipment
The JPS Customer Service Department can be reached by phone at [phone], or by email
to [e-mail]. Upon receipt of this information, JPS will arrange for repair or
replacement of the equipment.
2.3 Reshipment of Equipment
If it is necessary to return the equipment to the manufacturer, a Returned Material
Authorization (RMA) number must first be obtained from JPS, following the process detailed
on the JPS website. This number must be noted on the outside of the packing carton and on all
accompanying documents. When packing the unit for reshipment, it is best to use the original
packaging for the unit; if this is not possible, make sure that adequate packing material is used
to prevent excessive shocks during transport and handling.
Shipment should be made prepaid consigned to:
JPS Interoperability Solutions
Customer Service Department
5800 Departure Drive
Raleigh, North Carolina 27616
USA

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Mark plainly with indelible ink all mailing documents as follows:
GOODS RETURNED FOR REPAIR
Mark all sides of the package:
FRAGILE - ELECTRONIC EQUIPMENT
Inspect the package prior to shipment to be sure it is properly marked and securely wrapped.
2.4 Installation Overview
NOTE: QMT-1B installation requires knowledge of Ethernet network
fundamentals as well as a basic understanding of Internet Protocol (IP). As with any
network-connected device, improperly configuring and installing the QMT-1B
could disrupt proper network operation. Please seek the assistance of your network
administrator or other knowledgeable person if you are unsure about how your
network is configured.
Five steps are needed to properly install the QMT-1B. These steps are:
1. Determine the IP address, subnet mask, and (if applicable) the gateway address for
the unit. You may have to contact the network administrator for your organization to
obtain this information.
2. Provide the proper primary power for the unit.
3. Interconnect the unit with the communications system via the QMT-1B's rear panel
connectors. J6 provides the audio and control lines necessary to interface the QMT-
1B to your voting receiver and any system transmitter. J4 uses a standard RJ-45
Ethernet Patch Cable (non-crossover) to connect to the network.
4. Configure the unit’s operational parameters per the Configuration section of this
manual.
5. Set the input and output audio levels per Section 3.2.
The QMT-1B is then ready to use.

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2.5 Installation Considerations
Careful attention to the following installation suggestions should result in the best unit/system
performance. The QMT-1B must be installed in a structure that provides both protection from
the weather and assurance of ambient temperatures between -30 and +60 degrees C. When the
unit is mounted in a cabinet with other heat-generating equipment, the use of a rack blower is
suggested to keep the cabinet interior temperature rise to a minimum.
NOTE: If the QMT-1B is installed in a high RF environment such as repeater
system or other transmitter site, it is recommended that all cable assemblies be
individually shielded, with the shield grounded to the ground pin on the terminal
block for that module. For all D-subminiature connector cable assemblies, cable
shields should be connected to connector shells so that they make contact with the
grounded D-subminiature connector shells on the QMT-1B.
The unit is 1.36 inches tall, and 6.5 inches wide by 6.5 inches deep.
Figure 2-1 Front & Rear Panel Views

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2.5.1 Power Requirements
The QMT-1B is designed to operate from a nominal +12V DC supply. The unit will meet all
of its specifications over a voltage range of +11 to +15 VDC and will be damaged by a DC
source that delivers a constant (non-transient) DC voltage above this range. The DC power
consumption is 500 mA maximum. The AC adapter provided with the unit meets these
specifications.
The QMT-1B is a microprocessor-controlled device. As with any such equipment, a very short
loss of power can cause operational problems and/or cause the unit to reset. The
communications link will be inoperable during the reset period. JPS recommends the QMT-1B
and associated equipment be connected to an AC power source that utilizes an uninterruptible
power system (UPS). If the overall site does not have UPS capability, the QMT-1B should be
plugged into a smaller UPS, such as those used for personal computer systems
2.6 Installation Checklist
Table 2-1 Basic Installation Checklist
Determine QMT-1B network parameters
such as IP address, subnet mask, and
gateway address.
You must assign these values. If you are not sure
how to determine these values, see the network
administrator for your organization.
Provide suitable power for the device.
See Section 2.5.1 Power Requirements.
Make interconnections.
See Section 2.7.2 Audio Level Adjustment for
External Interconnect Information.
Configure QMT-1B parameters.
See Section 3 Configuration.
Adjust audio levels.
See Section 3.2 .
2.7 Rear Panel Connectors
The rear panel connectors are explained in the section below, starting at the left side of the
panel.
2.7.1 DC Input Connector
The QMT-1B operates on a nominal +12 VDC. The power is applied via the “Wall Cube” AC
adapter provided with the unit. The DC input is reverse polarity protected.
2.7.2 Audio Level Adjustment
The QMT-1B now uses internal “soft pots” for audio adjustment from a web browser. See
Section 3.2
2.7.3 Connection to Radio
The interface between the QMT-1B and associated radio is made via rear panel Audio/Control
connector (female DB-15). A mating male connector is included in the accessory kit; it breaks
out the DB-15 signals to screw terminals.

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2-5
Table 2-2 QMT-1B Audio/Control Port Pinout
PIN
Signal
Description
1
Ground
Ground connection.
2
Not used.
3
Not used.
4
E&M Return
Configured via jumper J13
5
Ground
Ground connection.
6
Audio Output
Balanced audio output A.
7
Ground
Ground connection.
8
Audio Input
Balanced audio input A.
9
Not used.
10
Not used.
11
Not used.
12
/PTT Output
Output to radio PTT, active low, relay contact to ground.
13
/COR Input
Input from radio COR, programmable active high/low.
14
Audio Output
Balanced audio output B.
15
Audio Input
Balanced audio input B.
2.7.3.1 Audio Input
The QMT-1B audio input is 600 ohm, balanced. It can be used as an unbalanced input by
grounding one half of the balanced pair and connecting the single-ended input to the remaining
half. Balanced inputs and shielded cables are recommended for superior noise immunity.
The audio input will accept signal levels from –26 to +10 dBm. Internal circuitry is used to
amplify or attenuate this input as necessary to optimize the level to the DSP. The signal level is
adjusted by the “RX input level” pulldown in the web interface Configuration page. The input
is set to -10 dBm when shipped. This mean an audio input level of -10 dBm is expected and
provides the correct level to the internal audio circuitry.
2.7.3.2 Audio Output
The audio output from the QMT-1B is a balanced 600-ohm output. The output level is adjusted
by the” TX output level” pulldown in the web interface Configuration page. This output
provides a -10 dBm nominal level into a 600-ohm load. The TX audio output will supply
signal levels from –26 to +10 dBm.
2.7.3.3 COR Input
The COR input to the QMT-1B is a high impedance input and can be programmed to be active
high or active low. In the active low configuration, the input is pulled up to +5V DC internally
through a 47K ohm resistor. In the active high configuration, the input is pulled down to ground

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through a 22K ohm resistor. The logic threshold is 2.5V DC nominal, and the input is protected
from momentary surges up to +100 V DC.
2.7.3.4 PTT Output
The PTT output from the QMT-1B is an E&M relay type that grounds the PTT output when
active. The PTT output can also be configured to be an open drain type which can sink up to
100 mA of current and can withstand open-circuit voltages up to +60V DC. In order to avoid
conflicts with internal pull-up resistors on the PTT lines of some radio equipment, there is no
internal pull-up resistor on the NXU-2B PTT output.
The QMT-1B is configured for E&M relay PTT when it leaves the factory.
2.7.3.5 E&M Return Selection
When the PTT source is set to use the internal relay, the user may select either an internal
GROUND as the return or an external pin on the Audio/Control jack as the return. This is for
E&M applications where some PTT reference other than ground may be desired. To select the
internal GROUND reference place J13 (E&M Return) in the Ground position. When an
alternative reference is desired place both J13 and J15 in the right position. The desired E&M
return voltage may then be applied to pin 4 of the Audio/Control jack.
2.7.4 Network Connection
The QMT-1B is connected to the Ethernet network via a standard Ethernet Patch Cable (non-
crossover, plugged into the rear panel RJ-45 connector.
2.7.5 RS-232
This connector currently has no field use with the QMT-1B application.

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2.7.6 Internal Jumper Configuration
The illustration below shows the QMT-1B internal PCB jumper locations. The only reason to
open the unit is if these default settings are not optimal for your system. For the majority of
applications, the default jumper settings are sufficient and need not be changed.
Figure 2-2 QMT-1B Internal Configuration Jumpers
Table 2-3 QMT-1B Jumper Settings [Default Settings in Bold Text]
Jumper and Function
Left 2 Pins
Right 2 Pins
J8: Audio In –Balanced/Unbalanced
Balanced
Unbalanced
J9: Audio In –Impedance
600 Ohms
High Impedance
J13: E&M Return
Ground
J6 pin 4.
J14: PTT Source
Transistor open
drain
Relay Contact
J15: J6.4 Pin Function
Not Used
E&M Return

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End of Section 2