
 MT125 & MT300 Sensor EX  
- 1- 
  Designation of MT Sensors are temperature measurements of devices like motors, controllers, 
batteries and other model accessories. Presentation of the measured data is realized by the JETIBOX 
terminal and the wireless information transfer is ensued with aid of the DUPLEX 2,4GHz system.  
  The Duplex System takes advantage of the 2,4GHz-Band for communication which allows not only 
the transfer of remote control data to the model, but also in the opposite direction to the transmitter. The 
telemetric data measured during operation are transmitted in real time and the actual state of the data can 
be depicted on the JETIBOX LCD-display. The MT unit records minimum and maximum temperatures of 
the individual sensors and delivers besides that their actual values.  
The JETIBOX terminal takes care of parameter adjustments as well as of indications of measured data. 
The MT device consists of two parts. In the first instance of the MT module itself, which is recording the 
data measured by temperature sensors connected to the MT module, which on the other hand can be 
connected to the JETIBOX, to a receiver or to an Expander of the DUPLEX system. Keep an eye on the 
temperatures of the module and sensors in order not to expose them to temperatures higher than allowable 
– see technical data table.  
  The MT module allows triggering of acoustic alerts by the individual sensors. These alerts can report 
of temparature limit violations by too high or too low temperatures exceeding adjusted limits. The 
acoustic signal is generated by the transmitter module DUPLEX Tx which contains a small siren. The 
signals are differentiated by Morse codes in order to be able to distinguish between the individual types of 
alerts referring to individual sensors. The acoustic signalling of parameter violations will be generated 
even if there is no JETIBOX available. With a connected JETIBOX there will be an indication on its 
display showing which parameter has been violated. If several parameters have been violated at the same 
time the alert sounds change consecutively as well as the indications in the JETIBOX LCD-display.  
Number of Temprature Sensors 
MT-Module Operation Temperature 
MT-Module & Sensor intrinsic consumption 
Connection of MT-Sensors 
  In the MT125 Module you will find two inputs for the connection of temperature sensors coded A 
and B. Connect the sensors to these inputs while paying attention to polarity (red sensor wire to + and the 
black one to - ). Constituent parts of the MT300 sensor are two sensors which comprise a loop of heat 
resistant conductor in the central part. A silicon tube sliding over the loop serves for fastening purposes. 
Fastening of the sensors 
Place the MT-Module as far away as possible from 
heat sources in order not to exceed the allowed 
maximum temperature.  
Sensors of the MT125 Module are able to measure 
temperatures up to 125°C. Fasten the sensor to the 
measured object as secure and tight as possible in 
order to prevent contact losses and herewith falsify 
measurement results. Choose a fastening method 
which corresponds to the assumed maximum 
temperature of the measured object. For low 
temperatures you may choose glue or shrink tubing 
(batteries, controllers etc.). In case of higher 
temperatures fasten the sensors by means of the 
enclosed plastic tape. 

 MT125 & MT300 Sensor EX  
- 2- 
Sensors of the MT300 Module can be used for higher temperatures (engine cylinders, engine exhausts 
etc.). The sensors are adapted to this purpose and comprise a loop of heat resistant conductor in the 
middle. Before tightening moisten the silicon tube with alcohol or white spirit in order to improve its 
sliding ability on the cables. Put the measuring object, for instance an engine cylinder, through the loop 
and tighten the loop strongly by means of the silicon tube in order to obtain a tight contact between the 
loop and the measuring object (for instance with cooling fins of an engine cylinder). After evaporation of 
the alcohol the silicon tube will firmly hold the loop tight. In order not to damage the sensor the dia. of 
the loop should not be smaller than 20 mm. 
Parameter adjustment of MT-Modules 
Parameter adjustment a data readout is accomplished by the JETIBOX terminal. After connection to the 
MT-Sensor there appears an identification of the sensor and in the second line the actually measured 
temperature data of both sensors. By long pushing down button R (right) a fast deletion of all measured 
parameters can be triggered. Fast deletion is indicated in the first line of the display by an asterix „*“. 
By pushing button D (downward arrow) of the JETIBOX you will enter the MT-Module menu. 
Menu of the MT-Module: 
MT125 MENU: ACTUAL VALUE – select presentation of actual measured data by pressing button D 
(down arrow) 
Actual Temp. A – presents the actual temperature of sensor A   
Actual Temp. B – presents the actual temperature of sensor B  
MT125 MENU: MIN / MAX – push button D (down arrow) in order to select the recorded extreme  
values which occured during measurements on both sensors.  
Temp. A  MIN / MAX – represents the minimum and maximum temperature value which has been  
recorded by sensor A during all measurements. 
Temp. B  MIN / MAX – represents the minimum and maximum temperature value which has been  
recorded by sensor B during all measurements. 
Records of all extremes can be deleted in the menu Setting - Erase Data. If you don´t delete all data  
records manually, the MT-Module will record the maximum and minimum sensor temperatures whether 
it has been in the meantime disconnected of the voltage supply or not, i. e. the presented data can concern 
preceding operations. 
MT125 MENU: Setting – by pushing button D (down arrow) the basic MT-Module adjustment will be  
selected. 
Erase Data – pushing buttons R and L (right and left arrows) simultaneously will delete all records of  
measured parameters (minimum and maximum temperature values of sensors A and B). 
Beep Temp. A – adjustment of a Morsealphabet character which will announce violation of the set alert  
temperature of sensor A by an acoustic signal of the DUPLEX Tx transmitter module. 
Beep Temp. B – adjustment of a Morsealphabet character which will announce violation of the set alert  
temperature of sensor B by an acoustic signal of the DUPLEX Tx transmitter module. 
MT125 MENU: ALARMS – by pushing button D (downward arrow) you will enter the adjustment  
modes of particular alerts. If violation of a set parameter occurs the indication of the JETIBOX LC 
display will show in the second line of the basic menu the original indication as well as the particular alert 
indication alternately and the siren of the transmitter module will emit alert signals. The first tone is a 
reference signal and the second tone is the corresponding Morse signal of the particular alert. There will 
be no particular signal emitted if the alert is in OFF position.  
Temp. High A – signal adjustment for high temperatures, if the measured temperature exceeds the set  
value alert of sensor A will be activated. 
Temp. Low A – signal adjustment for low temperatures, if the measured temperature is below the set value  
alert of sensor A will be activated. 
Temp. High B – signal adjustment for high temperatures, if the measured temperature exceeds the set  
value alert of sensor B will be activated. 

 MT125 & MT300 Sensor EX  
- 3- 
Temp. Low B – signal adjustment for low temperatures, if the measured temperature is below the set value  
alert of sensor B will be activated. 
MT125 MENU: SERVICE – by pressing button D (arrow down) you will change to depiction of the  
firmware version and to renewal of the sensor default setting. 
Factory Defaults – by simultaneous pressing of arrows R and L (right and left) the factory settings of the  
MT125 are loaded.  
MT125 v. xx.xx ID xxxxx:xxxxx – product marking with firmware version and series number (ID). 
Connection of the MT-Module 
1. The triple core cable with JR plug can be connected directly to the JETIBOX (socket with the coding 
pulse, +, - ). A supply voltage of 5-8,4V must be connected to the second JETIBOX input coded with (+, 
- ). The wireless data transfer is not working when wired up this way and measuring data are directly 
shown in the JETIBOX LCD display. This setup does not allow alert triggering due to the fact that the 
siren is a component of the transmitter module which is in that case not connected. Alert reports will be 
shown on the LCD-display only. 
2. Connect the triple core cable of the MT-Module with JR plug to the socket on the back side of the 
DUPLEX-receiver (coded with Ext.). The current supply for the MT-Module is delivered by the receiver. 
In order to adjust MT-Module parameters connect the JETIBOX to the transmitter module and switch on 
the DUPLEX receiver and transmitter. 
3. Connect the triple core cable of the MT-Module with JR plug to one of the EXPANDER inputs. The 
Expander allows connection of several telemetry sensors to one receiver. In that case the MT-Module gets 
its current supply via the Expander and the Expander via the receiver. 
Firmware Update 
The equipment firmware may be updated by a PC via the converter unit JETI USB Adapter. In the 
USB Adapter instructions you will find a description of the installation procedure of the USB Adapter 
controller as well as the update program.  

 MT125 & MT300 Sensor EX  
- 4- 
Warranty 
For this product we grant a warranty of 24 months from the day of purchase under the assumption 
that it has been operated in conformity with these instructions at recommended voltages and that it has not 
been damaged mechanically. Warranty and post warranty service is provided by the manufacturer. 
We wish you sucessful flying with the products of: JETI model s.r.o. Příbor, www.jetimodel.cz 
MT modul Menu as shown by the JETIBOX LCD: