The 5% increase from the second quarter saw sales reach £478m, said analyst Infonetics Research.
The analyst said year-on-year sales for carrier next generation voice kit are so far up 15%.
"The third quarter was marked by strong gains in soft switch, session border controller (SBC), and media server sales, driven by increasing demand for voice over broadband, said Infonetics analyst Stephane Teral.
"On the down side, we saw disappointing trunk media gateway deployments across categories, particularly at large North American cable firms, said Teral.
Nortel is the leading voice over IP soft switch vendor by revenue, followed by Nokia Siemens in second place, and Huawei in third, said Infonetics.