Python-DTMF Sender through SIM7600/SIP/VOIP

I'm currently in need of a dedicated Python developer capable of writing a specialized python script. Using Google Cloud Speech-to-Text, the script needs to recognize certain words from ongoing voice communication. Upon recognition of specified words, the code will need to send DTMF commands via a SIM7600 or SIP/VOIP system.

In order to accomplish this project's requirements:
- Proficiency in Python 3.5 is a must, as the script will need to be written fully in this version of Python.
- Familiarity with serial communication is key, as this will be the method through which the script interfaces with the SIM7600 or SIP/VOIP system.
- A thorough understanding of Google Cloud Speech-to-Text API is essential given its integral role in detecting specified words from speech in real-time.
- Experience with telecommunication platforms, particularly SIP/VOIP systems and SIM7600 modules, will be highly beneficial for successful completion of this task.

Only python developers with a deep understanding of these technologies should consider bidding for this project. I'm also hoping to find a freelancer who values clear communication and timely delivery. Please, include past similiar projects in your proposal.