There must be some more context to clarify if this is correct. The Belugyi szam would be Department of Interior number; the preposition depends on the context. Also, in some contexts the word szam may be translated as other than number (numeral, key, whatever). Whithout context this is my best guess.

Hungarian term (edited): Belügyi számon

If the entire line reads: 14-099 Belügyi számon, and this is also on that card that you asked about, you may want to match the word order to the other entries (business hours and such).

I know that my answer is a little bit different from those of my peers, but please, bear with me, and read the explanation. Belügyi is as short form for belügyminisztériumi (from the Ministry of Interior), however since the function of the Hungarian Ministry of Interior is different from the function of the U.S. Department of Interior, it would give the wrong association if we simply in. The function of the Hungarian Ministry of Interior is closest to that of the current Department of Homeland Security (you are familiar with it, because you are a U.S. resident), just like the function of Sigurimi in your home country. Now, regarding the phone line. I know of three organizations in Hungary (there might have been more) that had their internal phone network. These are the Ministry of Interior, Hungarian National Railroads, and Ministry of Defense. Apparently the cardholder is an employee of the Ministry of Interior, and is entitled to use the internal telephone network. Very important: not every Ministry of Interior employee was entitled to use the network, only those who had been given access. And the internal network was set up to assist primarily the people working for the Hungarian Homeland Security. If he was allowed to give out the internal network number, he was definitely linked to Homeland Security.

--------------------------------------------------
Note added at 3 days20 hrs (2009-12-19 00:32:14 GMT)
--------------------------------------------------

Here is some answer to the peer comments below, because it would not fit there. First of all in Hungary there is no Belügyminisztérium any more, because it was changed to Önkormányzati Minisztérium, but officially it was Ministry of Interior, at least by their own minister and the prime minister. See here: http://www.magyarorszag.hu/english/abouthungary/data/system/...
Yes, I agree, you can translate it Ministry of Internal Affairs, because this term is used in official English translations of Russia, Uganda, Liberia etc., but why go that far? The reason I used a US format is, because Monika lives in the U.S. and I presume that it is for an American client, plus the ILEA was set up by the U.S.A. in Hungary at the time of the political changeover. We translated a lot of material for them at that time, and this is how I know about the belügyi vonal. This is how I know that this special secure line was created to connect the police stations and other institutions of homeland security with the ministry and with each other. When we translate we try to use the most descriptive version, and I am convinced that mine was the most descriptive and true.