4G Voice Gateway With DTMF

@Mahihassi

As an Electrical Engineer with a Master's in Embedded Systems, I bring deep expertise in the exact fields your project requires. From designing robust hardware systems to developing firmware and integrating with network protocols, I've done it all. Assembled with proficiency in using a range of microcontrollers and embedded systems like STM32, ESP32, Texas Instruments, Raspberry Pi, Nordic nRF52/nRF53 and more; I've gained tremendous experience dealing with technologies that mitigate against challenges telephone gear would face during a transition from landline to a 4G network. My understanding of RF sections and knowledge of both PCB design and telecommunication engineering enables me to optimize your project for compatibility with Spark, OneNZ, and 2Degrees bands.

@MuhammadUzair16

I am an embedded systems engineer with over 16 years of experience. I have worked with a very similar project before but using 3G. I would like to know more about how you want the DTMF to be used as some of the full landline DTMF features are just not available on cellular network. I can provide you a full prototype with all design files to be able to produce more. I can adjust my pricing if needed based on what we discuss further. Please contact me to discuss details.

@ITECH

As someone with extensive expertise in Arduino, Electronics, Microcontroller, PCB Design and Layout, I believe I am the perfect fit for your "4G Voice Gateway with DTMF" project. My goal is to ensure that you transition smoothly and seamlessly from your copper landline to a reliable 4G solution. Working across IoT, automotive electronics and embedded systems has equipped me with a deep understanding of the complexities involved in translating diverse signals flawlessly. I have prior experience working with varied modems like Quectel and SimCom, ensuring they passed multiple certifications. In addition, our team at Product Development Services Under One Roof comprises professionals who can help expedite Nanodegrees. Therefore, I can guarantee clean voice quality minus clipping or delays in transmitting and recognizing DTMF as required. Being reliable is my topmost priority - if you choose me for this project, you can rest assured that you will have a thoroughly-tested prototype that demonstrates stable network registration on all three carriers

@mairajali11

With over 8 years of experience in electronic engineering, I believe I am the most suitable fit for your project. Given that my specialties lie in the exact areas your project demands - such as PCB Design and Layout, Telecommunications Engineering, and Arduino - I am confident in providing a scalable and reliable solution for your requirement to replace your landline with a 4G Voice Gateway. To ensure flawless performance, I plan to utilize reputable modems such as Quectel or SimCom, which will operate on the specific bands required by Spark, OneNZ, and 2Degrees networks. In adherence to your project deliverables, I will provide a comprehensive package including schematic, BOM and PCB layout, firmware source and compiled image, and an enclosure design suitable for manufacturing. Furthermore, my expertise goes beyond just creating a functional prototype. I thoroughly understand the importance of end-to-end testing to ensure stable network registration and voice quality on each carrier. To expedite the process, I can leverage my previous certifications and knowledge regarding regulatory standards in the industry. Let's connect to discuss your project details further!

@engrusmanfaiz

Hello, This is not just a modem design—it requires carrier-grade VoLTE handling, precise DTMF timing, and a stable FXS interface behaving like true PSTN. I have strong experience in embedded systems, RF-aware PCB design, and telephony/audio interfacing. I propose using Quectel EC25/EG25-G or SIMCom A7670 series (VoLTE-capable, multi-band support for Spark, OneNZ, 2Degrees). FXS will be implemented using a dedicated SLIC (e.g., Silicon Labs) to ensure proper line voltage, ringing, and impedance. DTMF accuracy will be handled via hardware-assisted generation/detection to avoid latency and clipping. Firmware will manage VoLTE sessions, call states, and SPI/UART control with robust error handling. PCB will be RF-optimized with controlled impedance, antenna matching, and EMC-conscious layout. Deliverables include full Altium design files, firmware, enclosure (STEP/STL), and tested prototype. I can also assist with PTCRB/GCF pre-compliance and carrier certification readiness. Regards, Muhammad Usman Embedded & PCB Design Engineer

@AITSoft

As an experienced software developer, I understand the value and technical acuity needed for your project. My diverse skill set includes deep knowledge in electronics, microcontrollers, PCB design and layout, all of which would be maximumly applicable to creating a 4G voice gateway with DTMF capabilities like you require. Specifically in Electronics, I have great experience with RF components and circuitry covering a wide range of frequency bands that should provide solid compatibility with the major carriers Spark, OneNZ and 2Degrees. Combining this with my proficiency in dealing and debugging large systems alongside my skills in motor control and data analysis should lead us into a successful project as we will be executing potentially thorough testing across each Nedwork possible. In addition to my technical expertise, I bring efficiency and promptness to completing projects. This adherence to timeliness is significant because it recognizes the burning need you might have as traditional copper landlines are decommissioned. That said, adhering to strict network protocols shouldn't present a challenge for me since I've previously completed similar projects just like yours proficiently.

@tshibsamuel477

Hi there, I carefully read your project, and I can help design a reliable 4G VoLTE-to-PSTN interface that allows existing telephone equipment to keep working through an RJ-11 FXS port. I’m Samuel Tshibangu, a mechatronics engineer with strong experience in PCB design, embedded systems, telecom modules, audio interfaces, and power/RF-aware hardware design. I’ve worked with similar architectures involving cellular modules, voice/audio paths, DTMF handling, SIM interfaces, and enclosure-ready electronics, so I can move quickly and deliver a practical prototype. For this project, I would focus on a proven modem platform such as Quectel or SimCom with VoLTE support, correct carrier band coverage, clean FXS interface design, reliable DTMF performance, and production-ready PCB/enclosure files. Feel free to send me a message. Best regards, Samuel Tshibangu

@AwaisChaudhry

With my extensive knowledge and expertise in both hardware and software development, I am confident I can deliver an exemplary solution for your 4G Voice Gateway project. At ZAWN Tech, we have a dedicated team specialized in electronics, microcontrollers, PCB design and layout. Our proficiency extends to embedded systems and automation, precisely the skills needed for creating the unit you require. Drawing from our experience of over a decade, we have developed a keen understanding of the need for reliability and precision in technology products. Your project demands a self-contained unit that will effectively allow for PSTN line-like functionality over 4G networks. This fits perfectly with our domain knowledge around Voice over LTE (VoLTE) calls and DTMF performance, ensuring error-free transmission without any clipping or delay. Moreover, our long-standing relationship with various carrier companies, including Spark, OneNZ, and 2Degrees will be valuable in aligning your product with their VoLTE profiles. We are committed to delivering clean voice quality and stable network registration on all three carriers—this stems from our unwavering focus on creating fast, secure, and scalable systems. With us at the helm of your project, you can rest assured that you'll have a prototype demonstrating exactly what you need—a robust 4G solution capable of accommodating multiple carrier profiles while preserving uncompromising call quality.

@leonidye

Hi, I can develop a compact 4G VoLTE-to-FXS gateway that works like a standard PSTN line, with reliable voice and accurate DTMF. I propose using a Quectel LTE modem (e.g., EC25/EG25-G) with a proper SLIC for RJ-11 interface, ensuring stable VoLTE operation across Spark, OneNZ, and 2Degrees. Deliverables: * Schematic, PCB, BOM (production-ready) * Firmware (VoLTE + DTMF handling) * Enclosure (STEP/STL) I also support certification and carrier compliance if needed. Best regards

@yaroslavmark

Hi I am an Embedded Hardware Engineer with 10+ years of experience in telecom and hardware design, and I’ve delivered 20+ cellular-based products including 4G gateways and VoLTE-enabled devices, with proven field deployments achieving >99.5% call stability and sub-50 ms DTMF detection latency. I recently completed a similar FXS gateway using Quectel EC25 and SimCom A7670 modules, ensuring carrier certification alignment and clean analog front-end performance. For this project, I will use a carrier-approved LTE Cat-4 module (e.g., Quectel EC25 or SimCom A7672S) with integrated VoLTE stack and design a precision FXS interface using a dedicated SLIC (such as Silicon Labs) to emulate PSTN characteristics accurately. My approach (1) RF and modem selection aligned with Spark, OneNZ, and 2Degrees bands and VoLTE profiles (2) robust schematic and PCB design with impedance-controlled RF layout and low-noise analog voice path (3) firmware development for AT-based VoLTE control and real-time DTMF handling/validation (4) enclosure and thermal design for stable operation (5) prototype validation including voice quality, DTMF accuracy, and multi-carrier registration testing. Questions : ✅Could you confirm whether you require battery backup for power outages? ✅Do you have a preferred SLIC vendor or should I select based on availability and performance? ✅Are there size constraints for the enclosure? ✅Do you need remote management or firmware update capability (OTA)? Best, Yaroslav

@Mahmoud00Ibrahim

Hi, I’m very interested in your project and can start immediately. I have solid experience in embedded systems, RF-aware PCB design, and telecom interfaces. I can develop a reliable 4G VoLTE-to-FXS gateway that behaves like a true PSTN line, including clean audio path design and precise DTMF handling. For the cellular side, I plan to use a proven LTE Cat 4 module such as Quectel EC25 or SIMCom A7670 series (both widely used and support VoLTE depending on firmware/carrier profiles). I’ll ensure band compatibility and VoLTE provisioning for Spark, OneNZ, and 2Degrees. The design will include: • Stable FXS interface (RJ-11) using a proper SLIC solution • Careful analog front-end design for voice clarity and impedance matching • Optimized RF layout for strong network performance • Robust firmware for call handling, DTMF accuracy, and network stability I can deliver the full package: schematic, BOM, PCB, firmware, enclosure (STEP/STL), and a fully tested prototype. I also have experience helping streamline certification (CE/FCC and carrier-related requirements) to reduce time to deployment. Happy to discuss the details and move quickly on this.

@tetianam8

⭐⭐⭐⭐⭐ I’ve built telephony gateways and can deliver a drop-in RJ-11 FXS box that behaves like a PSTN line while riding 4G. Platform choice (proven path): • LTE modem: Quectel EC25-AF (or EG25-G variant) — wide band support incl. NZ carriers; VoLTE-capable with operator profiles • FXS front end: Silicon Labs Si3217x — generates line voltage, ringing, impedance + integrated echo cancel • MCU/SoC: STM32 (control, audio routing, watchdogs) • Audio/DTMF: Hardware DTMF (in SLIC) + verified end-to-end timing; fallback detection in firmware • Power: 12 V input → isolated rails for SLIC + clean 3.3/5 V logic What you’ll get: • Schematic + 4-layer PCB (EMI-safe RF + audio separation) • JLC/PCBWay-ready Gerbers, BOM, CPL • Firmware (call control, VoLTE session, DTMF pass-through/regen) • Compact enclosure (STEP/STL) • 1 tested prototype with RJ-11 FXS: clean voice, accurate DTMF, stable registration on Spark / OneNZ / 2Degrees Milestones: Carrier profile + modem bring-up (VoLTE) FXS design (ringing, impedance, DTMF validation) PCB + enclosure Assembly, test report (audio THD, DTMF accuracy, call stability) Notes: I’ll target NZ bands and VoLTE profiles; can assist with PTCRB/RF pre-compliance planning. Quick questions: Single FXS port sufficient? Preferred input (12 V DC?) Any REN requirement for ringing load? Happy to build this into a reliable, carrier-friendly unit.

@electronicsdone

Best 4G VoLTE Voice Gateway Design Expert! ⭐⭐⭐⭐⭐ Dear Client, The biggest risk in this project is not building the gateway—it’s delivering a device that appears to register on 4G but suffers from unstable VoLTE behavior, poor audio quality, or unreliable DTMF performance when used with real telephone equipment. That is where telecom system design judgment matters. I would approach this by: 1. selecting a proven 4G LTE module (Quectel/SimCom) with full VoLTE support across your required bands and carrier profiles 2. designing a robust RF and baseband layout ensuring proper antenna matching, shielding, and stable network registration under varying signal conditions 3. ensuring precise DTMF generation and detection with no clipping, delay, or distortion during live calls This ensures the device is not just functional but delivers true PSTN-like reliability over 4G with stable voice and signaling performance. ✅Two quick questions: 1. Do you have any size constraints for the enclosure or antenna placement? 2. Should the design prioritize faster prototyping or certification-ready hardware from the first revision? If you message me, I can outline a complete hardware + system strategy to ensure reliable VoLTE and DTMF performance from the first prototype. Best regards, Prat PCB Must Innovations

@jaredj49

Hi, I’m a US-based certified electronics, embedded firmware, and RF engineer with extensive experience designing carrier-compliant cellular devices, including VoLTE-enabled FXS gateways and telephony interfaces. I have previously delivered end-to-end solutions that bridge legacy PSTN equipment to LTE networks, with a strong focus on carrier certification, RF robustness, and precise audio/DTMF handling. For this project, I will implement a proven LTE Cat-4/1 module (e.g., Quectel or SIMCom) with verified support for Spark, OneNZ, and 2Degrees bands and VoLTE profiles, ensuring stable registration and interoperability. The hardware design will include a high-quality FXS interface with proper impedance matching, ring generation, and codec tuning to guarantee clean voice paths and accurate, low-latency DTMF transmission and detection. I will deliver production-ready schematics, BOM, and PCB layout, along with optimized embedded firmware handling SIP/VoLTE stack integration, audio routing, and fault recovery. The enclosure will be designed for both rapid 3D prototyping and scalable injection molding, with attention to RF shielding, thermal performance, and usability. Finally, I will supply a fully validated prototype demonstrating reliable multi-carrier operation, excellent voice quality, and error-free DTMF performance, and can assist in expediting relevant regulatory and carrier certifications if required. Best, Jared

@Specgi

I can design and implement a reliable 4G Voice Gateway with full DTMF support, tailored to ensure seamless voice communication over cellular networks. The system will handle call routing, signal processing, and accurate DTMF tone detection for applications such as IVR systems, remote control operations, and automated services. I’ll ensure compatibility with SIP/VoIP systems, enabling smooth integration with your existing infrastructure while maintaining high call quality and low latency. With hands-on experience in telecom solutions and embedded or network-based voice systems, I focus on delivering stable, scalable, and secure implementations. Whether you need hardware integration, custom firmware/software development, or server-side configuration, I can provide a complete solution optimized for performance and reliability. My goal is to deliver a gateway that operates efficiently in real-world conditions while meeting your exact technical requirements.

@sakshis576

As an experienced freelancer in multiple technical domains, including PCB design and telecommunications engineering, I believe I bring a diverse skill set that is vital for this project. Alongside excelling in using Arduino, microcontroller, and electronics, my knowledge of using various modems and chipsets such as Quectel and SimCom could play a crucial role in ensuring the device's compatibility with Spark, OneNZ and 2Degrees network bands. In terms of the deliverables, my expertise in PCB design and layout hands me all the leverage to provide a well-structured unit for you. Additionally, my proficiency in 3D modeling/printing alongside my experience in developing enclosures can guarantee I deliver not just on the functional aspect but aesthetic as well. I'm fully committed to providing you with a high-quality product that serves its purpose efficiently. My approach has always been to thoroughly understand customer needs and deliver more than they expect. Choosing me would mean working with someone who can not only ensure a solid 4G solution but also guarantee error-free DTMF transmission and network registration stability across all carriers. Let's get your copper landline back on track with cutting-edge technology that keeps things simple!

@ElecHamza

Hi, I can develop a robust 4G VoLTE to PSTN gateway using the Quectel EG25G module to ensure full compatibility with Spark, OneNZ, and 2Degrees bands. I will design the hardware with a high quality SLIC and FXS interface to provide precise DTMF signaling and clear voice quality. My solution will include a custom PCB layout, firmware optimized for low latency, and a professional 3D printable enclosure. I have extensive experience in embedded systems and circuit optimization to ensure stable network registration and reliable telephone gear operation. I will provide a fully tested prototype along with all design files and the bill of materials ready for production. Best regards

@BenJeremie

As an experienced and thorough hardware and firmware expert, I believe I am the perfect fit for your project. My track record proves my commitment to delivering innovative solutions that align with my clients' unique needs. Designing varied PCBs for the last 8 years has given me the confidence to say that I'm familiar with your desired task; creating a self-contained 4G Voice Gateway with optimized DTMF performance. I plan on using the latest, reliable Quectel modems that pass Spark, OneNZ, and 2Degrees VoLTE profiles. My command on various PCB layout/software like Eagle, KiCad et al will ensure a solid RF section covering all necessary bands. Furthermore, my keen eye for detail, throughout designing & prototyping lifecycle, will help avoid hence eliminating potential clipping or delay issues. To provide a comprehensive solution, I also offer full support right from designing (schematic, BOM, PCB layout), validating to manufacturing – thus holding assurance of meticulousness at every stage. The end goal is always creating robust products - and having acquainted myself with your requirements and vision, working on this project together would be an absolute privilege. Let's get started!

@Ryan15222

Hi, I’m very interested in developing your 4G-to-PSTN (FXS) gateway. Delivering a unit that behaves like a true landline—with stable VoLTE, accurate DTMF, and carrier compatibility—requires careful hardware/firmware integration, which aligns closely with my experience. Proposed approach Use a proven LTE module such as Quectel EC25 / EG25-G (global bands, VoLTE-capable) or SimCom A7670 series depending on carrier certification needs Implement a dedicated FXS interface (e.g., Silicon Labs SLIC) to emulate a PSTN line (ringing, on/off hook, impedance, tone generation) Ensure precise DTMF generation/detection (hardware-assisted + firmware validation) Optimize audio path (PCM/I2S) for clean voice with minimal latency and no clipping Design RF section to cover Spark, OneNZ, 2Degrees bands with proper antenna matching Deliverables Schematic, BOM, and PCB layout (manufacturing-ready) Firmware (source + binary) with call control, DTMF, and SIM management Enclosure design (STEP/STL) for prototyping/production Fully tested prototype with RJ-11 FXS port meeting your acceptance criteria I can also support carrier certification (VoLTE profiles, PTCRB/GCF guidance) to streamline deployment. Relevant experience: Cellular IoT devices with LTE/VoLTE Analog telephony interfaces (FXS/DTMF) Embedded firmware for communication systems Best regards,