Most likely it's 2.4 ghz or 5 ghz and thus today I'm passing on a little tip to anyone in the market for portable phones for the office.
2.4 ghz is a very popular frequency for microwave ovens, phones and Wi-Fi. 5 ghz is increasingly popular with the soon-to-be new Wi-Fi standard, 802.11n (currently known as pre-n). It's also popular with other wireless technologies like Wi-Max.
I recently moved into a new apartment and at the same time had to invest in a new portable phone for my home office. Not knowing what signals may be beaming through my common walls, I made a point of buying a 6.0 ghz phone to avoid interference.
The new "n" standard is becoming increasingly popular and, unlike it's predecessors, is more likely to cut through common walls and across parking lots to infiltrate your space.
For those of you who found my headline a little obtuse today, it's a reference to Dan Rather's mystery mugging back in the late 80's. He claims a crazy man jumped him on the street's of Manhattan screaming "What's the frequency, Kenneth?". The band, R.E.M, immortalized the event with their hit song by the same name.