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The Arduino Telephone Caller ID Unit is a do-it-yourself display that reads caller-identification data sent over an analog telephone line. It uses an Arduino UNO, a custom HT9032D decoder module and a 16×2 HD44780 LCD. It is not a plug-and-play universal adapter: whether it works depends on the signaling used by your telephone provider and on what the project’s sketch handles.
What the Arduino Telephone Caller ID Unit does
The project is designed to display the telephone number and date/time information delivered by a telephone exchange. Its documented hardware combines an Arduino UNO with a custom HT9032D module and a 16×2 character LCD. The repository includes the Arduino sketch and module design files, and points to schematics and Gerber fabrication files in its release. Project repository
In broad terms, caller ID arrives as data encoded in audio-frequency signals on an analog telephone connection. The decoder module is intended to detect and interpret that signaling; the Arduino sketch processes supported packet data and the LCD presents it.
Will it work on your telephone line?
That cannot be assumed from the project description alone. Telephone companies may use different caller ID services, signaling conventions and timing, and the project discussion describes testing on a Swiss network while noting that differences elsewhere can affect operation. Confirm that caller ID is enabled on your line and check which signaling format and timing your provider uses before building around this design. Project discussion
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The module documentation lists Bellcore 202 and ETSI V.23 AFSK support, ring detection, and parsing for MDMF and SDMF caller ID and message-waiting data. That is a module-level description, not a promise that the entire Arduino project processes every listed message. The README says the current sketch handles MDMF caller line ID, name and date/time packet IDs. If you need SDMF or message-waiting messages, verify that the firmware actually handles them before relying on the display.
The project PDF gives a ring-detection range of 17 to 70 Hz above voice voltage levels. That figure describes this project’s documentation; it is not a general standard for every telephone network. Project documentation
Rank #2
- 1602 LCD screen can display 2 lines x 16 characters, with i2c serial interface, blue display.
- Built-in independent potentiometer, backlight can be adjusted through the back potentiometer.
- Power supply: 5v; I2C address: 0x27; wiring method: GND—GND, VCC—VCC, SDA—A4, SCL—A5.
- Compatible with most development boards, such as Arduino, Raspberry pi, Tinkerboard, Nano pi, Banana pi, stm32, etc.
- Widely used in: Internet of Things, school electronics projects, smart buildings, maker DIY projects, etc., can display letters, characters, numbers, real-time clock or temperature.
What parts do you need?
The display-unit build list calls for an assembled HT9032D module, an Arduino UNO, a 16×2 HD44780 LCD, a 2N3904 or equivalent NPN transistor, a 50 kΩ trimpot, 560 Ω and 22 kΩ resistors, and small breadboard(s). The decoder module itself is a custom board, not an established off-the-shelf plug-in component.
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The module parts list specifies an HT9032D DIP-8, 3.58 MHz crystal, RJ11/6P6C right-angle PCB socket, bridge rectifier, capacitors and resistors. The project says it uses standard through-hole components and publishes module design files, so sourcing parts and fabricating or assembling the board are part of the project. The documentation does not establish availability of a ready-made HT9032D module or endorse substitutes beyond the stated transistor equivalent.
Rank #3
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How to approach the build
- Check the line first. Confirm caller ID service is active and determine the signaling and message format used by your provider.
- Review the project files. Use the repository’s sketch, schematics, module design and release fabrication files to understand what must be built and which firmware behavior is documented.
- Assemble the decoder module. Obtain the listed components and build or fabricate the custom HT9032D board; the project’s display-unit parts list assumes this module is assembled.
- Connect the Arduino and LCD according to the project schematic. The published parts list alone does not specify pin-by-pin wiring, so follow the project’s actual design files rather than inferring connections from the parts names.
- Test only with appropriate telephone-line precautions. Confirm the display against calls on the intended line and troubleshoot compatibility if caller data is absent or incomplete.
How to decode caller ID FSK—and what this project covers
FSK caller ID decoding is not just a matter of detecting that a call is ringing. The receiver must work with the line’s signaling method and timing, identify the transmitted message format, and then handle the relevant data fields. This project assigns signal decoding to the HT9032D module and message processing/display behavior to the Arduino sketch.
- Protocol: the module documentation names Bellcore 202 and ETSI V.23 AFSK.
- Message format: the module documentation mentions MDMF and SDMF parsing, while the sketch description specifically names MDMF caller line ID, name and date/time packet IDs.
- Line behavior: provider-specific service and timing can determine whether the module receives usable data.
Those distinctions matter when adapting the design: matching the module’s claimed signaling support does not by itself establish that the sketch will display every message type your provider sends.
Rank #4
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- EASY INTEGRATION: 8-bit parallel interface and 28-pin module enable fast conmmunication to Arduino Uno R3 Uno R4 Mega Due Giga R1 and other Uno Mega form factor boards
- WIDE VOLTAGE COMPATIBILITY: Works with both 3.3V and 5V Arduino boards for flexible project integration
- LIBRARY AND TUTORIAL PROVIDED: Search for "DIYables TFT Touch Display Shield" for complete library, code and tutorials
Telephone-line safety and connection limits
An Arduino Forum test-tool post warns against connecting a PC directly to a live telephone line and cautions that ring voltage may exceed 90 V AC. Treat that as a concrete hazard warning, not as a complete safety standard. Do not attach a PC directly to a live line, and check your provider’s requirements and applicable local rules before connecting a homemade device. The available project sources do not establish certification for all networks or jurisdictions. Arduino Forum discussion
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