Portable FM Display Transmitter
LT-700

Highlights

  • Superior Audio Quality – 80 dB signal-to-noise ratio, setting the industry’s sound quality standard.
  • A choice between 57 channels, complete antenna and accessory options make Listen products ideal for a wide range of applications.
  • Look & Listen™ LCD shows channel, battery status, and programming information.
  • 100 % Digital – Listen receivers are digitally-tuned so transmission won’t drift; assurance that when you select a channel, it stays on the channel.
  • Transmit up to six (6) channels simultaneously on 72 MHz, three on 216 MHz.
  • Uses standard alkaline or NiMH batteries.
  • Transformer charging plug or drop in charging contacts.
  • Built in SmartCharge™ won’t allow batteries to overcharge. Charging circuitry is conveniently built into Listen’s LT-700 Transmitter; never worry about unplugging a transformer at a certain time.
  • Mute switch.
  • Mic and/or line level inputs.
  • Limited Lifetime Warranty with hassle-free support.

Overview

The Listen LT-700 Portable Transmitter is used to wirelessly broadcast audio for a variety of portable applications. Whether its voice or music, you can broadcast your audio to everyone in the audience without having to carry a microphone or be plugged into a wall. The LT-700 is excellent for factory tours, outdoor events, wireless microphone applications, classrooms, training, or personal use – anywhere you need to amplify sound, but don’t have (or want) an installed system. With the many features of the LT-700, portable transmission has never been easier for users!

Includes

(1) LT-700 Portable Display FM Receiver
(1) Owner’s manual (72 MHz and 216 MHz)

Configurations

LT-700-072 Portable FM Display Transmitter (72 MHz)
LT-700-216 Portable FM Display Transmitter (216 MHz)

Architectural Specs

The portable FM transmitter shall be capable of broadcasting on 57 channels. The unit shall incorporate a microphone sensitivity switch. The device shall broadcast on both wide and narrow band channels with a SNR of 80 dB or greater. The device shall have an audio frequency response of 50 Hz to 15 KHz, ±3 dB at 72 MHz, or of 50 Hz to 10 kHz, ±3 dB at 216 MHz. The device will incorporate a mute switch. The battery door shall be capable of being mechanically locked. The device shall incorporate an LCD display that indicates channel, battery level, low battery, battery charging, and RF signal strength. The portable transmitter shall incorporate automatic battery charging circuitry for recharging of NiMH batteries, with the ability to charge via a wall transformer or drop in charging case. The Listen LT-700-072 or LT-700-216 is specified.

CAD Drawing

    • Line Drawing



    1. A microphone or line level source (such as a CD or MP3 player) connects here. Use the LA-263 Line/Microphone “Y” Cable (72 MHz and 216 MHz) to connect an audio device with your microphone. Transmitter antenna is built into the microphone cord, eliminating additional wires while maximizing transmission effectiveness.
    2. Multifunction LED indicates when microphone is muted, if batteries are low, and charging status.
    3. Easy access mute switch.
    4. Look&Listen™ LCD Display shows channel selection, channel lock, and battery level.
    5. Offers 57 channels, or can be programmed so that only the channels you are using are displayed.
    6. Easy access POWER button.
    7. Uses two AA batteries. Adjustable to use either alkaline or NiMH batteries
    8. When enabled, SQ technology provides the highest audio quality available in its product category. SQ can be disabled for compatibility with other assistive listening or tour group equipment.
    9. Adjustable microphone sensitivity switch for best audio results.
    10. UP/DOWN channel selection. Also used to lock and unlock channel selection to prevent accidental channel switching.
    11. Manually lockable battery compartment door. 
    12. Single transformer charging plug port.
    13. Contact points for Listen’s drop in charging cases.
    14. Exclusive belt clip “loop” prevents unit from slipping off belt or strap.

    Specifications

     SpecificationsLT-700-072 LT-700-216
    RFRF Frequency Range72.025 - 75.950 MHz                          216.0125 - 216.9875 MHz
    Number of Channels17 wide band, 40 narrow band                                                             19 wide band, 38 narrow band 
    Number of Simultaneous Transmitters63
    Frequency Accuracy± .005% stability 32 to 122º (0 to 50ºC)
    Transmitter Stability50 PPM
    Transmission RangeFrom 0 to 150 ft. (45.7 m)
    Output PowerLess than 10mW (72 MHz)                 Less than 100mW (216 MHz)
    AntennaMicrophone cable
    Antenna Connector3.5 mm connector
    ComplianceFCC Part 15, Industry Canada
        
    Audio** All system specifications are wireless end to end**
    System Frequency Response50 Hz - 15 kHz (±3dB) 72 MHz, 50 - 10 kHz (±3dB) 216 MHz
    System Signal to Noise RatioSQ enabled: 80dB; SQ disabled 60dB
    System Distortion<2% total harmonic distortion (THD) at 80% deviation
    Microphone InputUnbalanced, ring of 3.5 mm connector, (-10dB nominal input level adjustable, +4dBu maximum, impedance 10k Ohms)
    Microphone SensitivityThree position switch: high, middle, and low; 6db increments
    Line InputUnbalanced, ring of 3.5mm connector, -10dbu nominal input level, -3dbu maximum, impedance 10K ohms
    Microphone Power3VDC Bias
      
    ControlsUser ControlsPower, mute, channel UP/DOWN
    Set-up Controls (battery compartment)Mic sensitivity, NiMH/alkaline battery, SQ enable/disable
    ProgrammingChannel Lock out,Channel lock
        
    IndicatorsLEDRed, illuminated when unit is on. Flashes when batteries are low, or to indicate charging. Flashes when muted
    DisplayChannel Designation, lock status, signal strength indication, battery life, RF Power
        
     Battery TypeTwo AA batteries, alkaline or NiMH
    PowerBattery Life (Listen batteries)20 hours alkaline (LA-361), 10 hours NiMH rechargeable (LA-362)
    Battery Charging (NIMH only)Fully automatic, 13 hours
    Power Supply I/P 120VAC; O/P 7.5VDC 250 mA; Drop in contact points for use with charging cases. Power supply not included (LA-202)
    Power Supply Connector2.3mm OD by 0.7mm ID, barrel type connector 7.5 VDC, center positive <250mA. Drop in contact points for use with Listen charging cases
    Power Supply ComplianceRoHS, WEEE, UL, PSE, CE, CUL, TUV, CB compliant
        
    PhysicalDimensions (H x W x D)3.00 x 1.00 x 5.00 in. (7.6 x 2.5 x 13.0 cm)
    ColorDark Grey with white silk screening
    Unit Weight3.9 oz (111g)
    Unit Weight with batteries5.8 oz (164g)
    Shipping Weight1.0 lbs. (0.45kg)
    DoorManually lockable, controls accessible through doors
        
    EnvironmentalTemperature - Operation14 to 104º F (-10 to 40º C) 
    Temperature - Storage-4 to 122° F (-20 to 50° C)
    Humidity0 to 95% relative humidity, non-condensing
        
    Specifications are subject to change without notification

    Requirements

    Used With

    Accessories

    Support Documents

    • FAQ

    What is the range of the LT-700 portable transmitter?
    Line of site up to 150 ft. (45.7 m) for both 72 MHz and 216 MHz. Line of site up to 200 ft. (60.9 m) with 863 MHz.  

    Can I have multiple transmitters operating in one facility?
    Yes. You can have multiple transmitter operating in one area on different channels, however more than one transmitter cannot be used on the same channel.

    Can I use a line source with the portable transmitter?
    Yes. Listen offers the LA-263, a mic/line input cable for this use (72 MHz & 216 MHz).

    How long do the batteries last on the portable transmitter?
    Alkaline batteries last 20 hours; NiMH rechargeable batteries last 10 hours (72 MHz & 216 MHz). With 863 MHz, Alkaline batteries last 15 hours and NiMH rechargeable batteries last 8 hours.

    Does the LT-700 provide phantom power?
    Yes, 3VDC.

    Will the LT-700 portable transmitter work for two-way communication?
    No. However, Listen does not recommend a two-way system for tour group applications. A two-way system means that everyone hears every sniffle, cough, comment etc. The tour guide loses control of the tour and the tour becomes unproductive.

    Troubleshooting Guide

    What is the range of this transmitter?

    • A range of up to 150 feet is achievable depending upon the following:

      • The orientation of the Microphone cord, which is the transmitting antenna.
      • The objects between the transmitter and receiver. All material, especially metal, will weaken the signal strength.
      • The type of receiver and its receiving antenna.

    What channels should I be transmitting on?

    • It is recommended that wideband channels are used for best audio quality. If transmitting multiple simultaneous channels, narrowband frequencies may be required.

    The signal being transmitted is inconsistent, my receivers cut in and out.

    • The receivers may be out of range of the transmitter.

    How do I connect my TV, VCR, CD player, etc. to this transmitter?

    • Listen provides a Line Input Cable (LA-263) that will allow you to connect an RCA connection to the transmitter.

    My microphone sounds very low in audio level.

    • Make sure that the microphone sensitivity switch, located in the battery compartment, is in the correct position. Consult the microphone users manual for the correct setting.

    What type of microphones can I use with this transmitter?

    • Any Listen condenser microphone may be used with this transmitter.

    My batteries will not charge.

    • Make sure you are using NiMH batteries.
    • Make sure the battery select switch, located in the battery compartment, is in the NiMH position.
    • Make sure that the power cord is plugged in properly.
    • If using a charging case, make sure that the transmitter is properly placed in the charging pocket.

    The batteries in my transmitter will not hold a charge.

    • It is time to replace the batteries. Listen recommends that the batteries be replaced every 3 years or after 500 charges.
    • Make sure that the transmitter is actually receiving the charge. The red LED on top of the transmitter will flash when charging.
    • Make sure that the unit is being turned off when not in use.

    When I use the mute function, the auxiliary input can still be heard.

    • The Mute function only mutes the microphone input. Any auxiliary audio input will still be transmitted.

    How do I lock out channels?

    • Enter the program mode by holding the UP and DOWN buttons simultaneously for 5 seconds. The PGM icon will appear. Once in the program mode, scroll through the channels using the UP and Down buttons. Briefly pressing the power button will toggle each channel in and out of Lockout. When the channel is locked out, the L/O will be displayed on the LCD indicating that channel is locked out.

       

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