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Senior Telephony Developer (SIP)

Senior Telephony Developer (SIP)

Objective of the Role

Semafone are looking for an accomplished telephony technologist, with excellent technical skills and extensive experience in the design and development of SIP-based solutions using tools such as Kamailio and Asterisk. You should be experienced in designing and delivering telephony/SIP based solutions and devising integration strategies and solutions for customer environments. You will have a passion for your chosen specialist areas and be actively striving to improve your skills, both at work and in your personal interests. You will thrive in a demanding technical environment that offers challenging and rewarding development work and feel a sense of satisfaction in getting the job done and delivering client value. 

Key Accountabilities and Responsibilities

  • Technical design and delivery of enhancements to Semafone’s core product offering and hosted services.
  • "Hands on" development and technical leadership and the mentoring of less experienced developers. Provide technical direction and support to expand Semafone’s product offering and expertise to the development team and the rest of the business.
  • Participate in all stages of the development lifecycle of the product, including requirements gathering, functional and technical designs, as well as programming and testing.
  • Act in a client-facing capacity as and when the need arises.
  • Offer second line assistance to the client support team, and in so doing, resolve client reported issues in a responsive and timely manner. 

Key Competencies

  • An excellent understanding of Telephony Solutions: OpenSER/ Kamailio & Freeswitch / Asterisk
  • Speech Recognition Technologies
  • VoIP SIP and RTP Telephony protocols
  • IP Networking knowledge is required (TCP/IP, UDP, Subnetting and Routing)
  • Virtual Machine Environments , ESXI VMware , Proxmox , KVM
  • Very strong communication skills especially when dealing with clients and including presentation skills
  • Ability to produce high quality technical documentation and user guides as required

Mandatory Qualifications, Skills and Experience

  •  Ideally a degree in a related computer or networking discipline or suitable industry experience.
  • 10 years in a software telephony based product development environment.
  • Ability to design and build mission critical (carrier grade) telephony systems, which are highly resilient, fault tolerant and scalable.
  • Deliver software in accordance with a PA DSS (audited software development process).
  • Self-starter, who can work remotely as well as in the office environment.

Desirable Qualifications, Skills and Experience

 Any experience in the following is highly desirable:

  • Web Applications , Jboss , Java development
  • RDBMS (MySQL / Oracle)
  • ISDN (European & North American variants)
  • Cisco Integrated Services Routers, SBCs
  • AWS and cloud technologies

Benefits & Culture

We are a market leader in secure voice transactions and trusted by our customers and partners.  We are on a journey to secure all personal data.  We recruit diverse, ambitious, innovative people who want to grow in a supportive and collaborative environment.  We are passionate, work hard, have fun and celebrate success.  Based in central Guildford, right by the station, in beautiful custom-fitted offices.

What we'll give you;

  • 25 Days Holiday, rising to 28 with service
  • Competitive Salary
  • Up to 10% Bonus
  • 4 x Salary Life Insurance
  • Vitality Health Insurance
  • HealthShield Cash Back Plan
  • Employee Assistance Programme
  • Bespoke Discounts and Communications Hub
  • Up to 5% Contributory Pension

Semafone is well funded and growing fast, you’ll be joining an organisation that combines an entrepreneurial ‘start-up’ culture with the professionalism of a mature and established business. This is a fabulous opportunity to gain experience on a variety of commercial matters of an international business.

*All final interview candidates will be subject to a DBS check as a pre-condition of a potential offer of employment. Any information found will be considered when making the final hiring decision. Please be aware that the background check process will not go ahead without your written consent.

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Pannell House
GU1 4HN Guildford Directions info@semafone.com 0845 543 0822

More than just a job...

Here at Semafone it's all about delivery and we pride ourselves in providing a flexible working environment which aims to support our staff as they journey through their career.  

For country-specific benefits check out each job role, but what else do you get besides your all important salary?

  • Bespoke Discounts & Communications Hub

    perkSTIR is our internal communications hub which houses a whole host of retailer discounts where you can literally save £/$000's a year!

  • Work / Life Balance

    We offer excellent time off benefits and promote flexible working whenever we can.

  • Great Physical Space

    We've got fabulous new offices in all locations. All mod-cons and tech'd up to the rafters it's a technologist's dream location.

  • Team Events

    We regularly get together as either individual teams, location-specific or the whole business. A highlight is our annual offsite, 'FraudSTIR' which involves internal and external presentations, team-building activities and lots of opportunities for socialising!

Workplace & Culture


Our company values aren't just words on a page to us.  They're intrinsic to the way we operate and vital to our success.  When they're effectively demonstrated wonderful things happen, so it's no wonder we recruit to our values and culture.


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