used at the NSA headquaters and at the office of the British prime minister. Nortel was a big Canadian telephone equipment manufacturer, but was dissolved in 2009. The Enterprise Voice and Data division of Nortel was bought by the US telecommications company Avaya (formerly Lucent)
The red telephone seems to be a phone from the UD-series of the Taiwanese manufacturer Uniphone, but remarkable is that it has no cord! That makes it looks like this phone was placed there more like a prop, demonstrating the (military/nuclear) power of the Israeli prime minister.
However that may be, in the video below we get an ever closer look at the red phone set. There it sits next to two black phones, one used by Netanyahu for calling the Russian president:
Israeli prime minister Netanyahu calling the Russian prime minister Vladimir Putin
thanking for Russia's assistance in fighting the fire in Israel's North
(December 3, 2010)
The flat black phone is the Telrad Executive Phone 79-100-0000 from the Israeli telecom equipment manufacturer Telrad. This phone can also be seen at the sitting corner of the prime minister's office and in the office of the defense minister. Therefore that phone must be part of the internal private branch exchange (PBX) system of both ministries. At least at the desk of the prime minister they were replaced by the Nortel M3904 by November 2012.
It's not clear what the red telephone is for, but a likely option is that it's connected to a military command and control telephone network, just like the Defense Red Switch Network (DRSN) in the United States, for which long ago also red phone sets were used.