of radio scanners in the United States varies considerably between jurisdictions, although it is a federal crime to monitor cellular phone calls. Five U.S. states restrict the use of a scanner in an automobile. Although scanners capable of following trunked radio systems and demodulating some digital radio systems such as APCO Project 25 are available, decryption-capable scanners would be a violation of United States law and possibly laws of other countries. A law passed by the Congress of the United States, under the pressure from cellular telephone interests, prohibited scanners sold after a certain date from receiving frequencies allocated to the Cellular Radio Service. The law was later amended to make it illegal to modify radios to receive those frequencies, and also to sell radios that could be easily modified to do so. This law remains in effect even though no cellular subscribers still use analog technology. There are Canadian and European unblocked versions available, but these are illegal to import into the U.S. Frequencies used by early cordless phones at 43.720–44.480 MHz, 46.610–46.930 MHz, and 902.000–906.000 MHz can be picked up by many scanners. The proliferation of scanners led most cordless phone manufacturers to produce cordless handsets operating on a more secure 2.4 GHz system using spread-spectrum technology. Certain states in the United States such as New York and Florida, prohibit the use of scanners in a vehicle unless the operator has a radio license issued from the Federal Communications Commission (FCC) (Amateur Radio, etc.) or the operator's job requires the use of a scanner in a vehicle (e.g., police, fire, utilities). Many scanner user manuals include a warning saying that, while it is legal to listen to almost every transmission a scanner can receive, but there are some that persons should not intentionally listen to (such as telephone conversations, pager transmissions, or any scrambled or encrypted transmissions) under the Electronic Communications Privacy Act, and that modifications to do so are illegal. In some parts of the United States, there are extra penalties for the possession of a scanner during a crime, and some states, such as Michigan, also prohibit the possession of a scanner by a person who has been convicted of a felony in the last five years. Many people including siren enthusiasts, aviation enthusiasts, and more use scanner audio or footage and post them online. Older people who are involved in these group (mainly siren enthusiasts)