The FNIRSI DSO-TC4 is a compact 3-in-1 handheld instrument that combines:

1. Digital oscilloscope
2. Transistor / component tester
3. Signal generator

in a single portable device.

With 10 MHz analog bandwidth, 48 MSa/s sampling rate, ±400 V input protection, and a built-in transistor/component tester plus waveform generator, it’s aimed at electronics repair, hobby, and R&D work where you want benchtop-style functions in a small, affordable package. 

Features :

• Oscilloscope
  
  • Bandwidth: 10 MHz
  • Sampling rate: 48 MSa/s real-time
  • Max input protection: ±400 V
  • One-key AUTO setup for fast waveform capture
  • Waveform screenshot storage & playback 
• Transistor/component tester
  
  • Automatic identification and measurement of:
    
    • BJT transistors, MOSFETs, JFETs, SCRs, triacs
    • Diodes, Zener diodes
    • Resistors, capacitors, inductors
  • Shows key parameters such as pinout, gain (hFE), threshold, leakage, ESR, etc. 
• Signal generator
  
  • Built-in function generator for test signals at the output port
  • Supports standard waveforms (e.g. sine, square, etc.; exact set varies by firmware/version) suitable for basic injection and testing in low-frequency circuits 
• 2.8" color TFT display
  
  • 2.8-inch TFT color screen for waveform and data display
  • Shows oscilloscope traces plus numeric readouts and test results clearly 
• Smart burnout protection
  
  • Internal protection circuits safeguard the device during measurement, including capacitor-discharge protection when testing charged capacitors (still recommended to discharge manually first).
• Multi-language UI
  • Supports 8 languages in the system menu (English + others), making it usable in many regions.

Specifications :

• Display: 2.8" TFT color screen 
• Front-panel controls (as labeled in the manual):
  • Power / return button
  • AUTO measurement button
  • Run/Pause button
  • Mode switch (oscilloscope / tester / generator)
  • Arrow/OK button area for menu and parameter adjustments
  • 1-2-3 transistor/component test socket
  • Infrared detection port
  • Voltage (oscilloscope) input interface
  • Signal generator output port
  • Oscilloscope channel interface (BNC, used with P6100 probe) 
• Power & charging:
  • Built-in rechargeable lithium battery (capacity varies in listings but is generally sized for long portable use)
  • USB Type-C for charging and possibly firmware updates 
• Measurement Ranges (from typical listings)
  
  • Resistance: approx. 0.01 Ω – 50 MΩ
  • Capacitance: approx. 25 pF – 1000 µF
  • Inductance: approx. 10 µH – 1000 mH
  • Oscilloscope: 10 MHz bandwidth, 48 MSa/s, ±400 V max input (with P6100 probe and proper settings)

Applications :

• Bench & hobby electronics
  • Quick visual check of microcontroller signals, PWM, and serial waveforms (within bandwidth)
  • Verifying audio signals, oscillators, and filters
• Repair & maintenance
  • Rapid testing of transistors, MOSFETs, diodes, Zeners, and passives during board repair
  • Checking power stage components by measuring ESR of capacitors and identifying faulty semiconductors
• Education & field work
  • Teaching basic oscilloscope and component-testing concepts with an all-in-one portable unit
  • Field diagnostics where carrying separate scope, LCR, and generator would be inconvenient

Important Notice: Make sure to fully discharge all capacitors before testing. Connecting charged capacitors can damage the device's internal circuitry, and any such damage will void the warranty.