Last Updated on April 19, 2023 by Dave Farquhar
If you are wondering about cordless phone frequencies, there are seven bands that have been in use since the 1980s. You can still buy phones for four of those frequencies.
There are two reasons to be concerned about a cordless phone’s frequency. The first is interference. Some phones interfere with other devices, such as wi-fi. The other reason is security.
The 7 cordless phone frequencies
Without further ado, here are the seven frequencies cordless phones use:
- 1.7 MHz, AM modulation
- 27 MHz, FM modulation
- 43–50 MHz, FM modulation
- 900 MHz
- 1.9 GHz, the DECT 6.0 frequency
- 2.4 GHz
- 5.8 GHz
Way back in the ’80s, early cordless phones picked up interference from such mundane things as fluorescent lighting. Eavesdropping on them was trivial as well. A police scanner easily picks them up. Sometimes even a regular radio will pick them up.
That was part of the sales pitch for 900 MHz phones. But today, when you can find a new 900 MHz phone, they usually do little or nothing for privacy since modern 900 MHz phones tend to be analog rather than digital.
1.9 GHz phones, also known as DECT 6.0 phones, offer the best combination of security and privacy and lack of interference. If you’re buying a new phone today, look for a DECT 6 phone.
2.4 GHz and 5.8 GHz phones interfere with wireless networks. As widespread as wireless networks are today, it’s best to avoid them for that reason. They were great in their time, but then wireless networks pre-empted them.
More GHz is better, right?
Marketers have trained us to think of more GHz as better, but with cordless phone frequencies, that’s not always the case. Higher GHz can mean better coverage, but interference is also important. That’s why marketers invented the term DECT 6 to make 1.9 GHz sound better than 5.8. It is better than 5.8, but 1.9 is less than 5.8, so they had to change terminology. So when buying a cordless phone today, don’t worry about frequency. Just get a DECT 6 phone and make sure it has some security features on it.
Security features associated with cordless phone frequencies
There was a time when I could tell you to just buy a phone at a certain frequency and be done with it. That’s not true today. Security costs money and nobody wants to pay $300 for a cordless phone anymore. But since security costs money, it probably means you don’t want the cheapest cordless phone on the shelf.
At the very least, a phone needs Digital Spread Spectrum (DSS) to make it harder to eavesdrop. By spreading the signal across multiple frequencies, reconstructing the conversation becomes too difficult for most troublemakers.
Better yet, look for a digital phone with an encrypted signal. A digital, encrypted signal is more difficult to intercept and listen to. I won’t say impossible, but your friendly neighborhood troublemaker doesn’t have that capability.
Keep in mind that law enforcement can listen in via wiretapping regardless of the type of phone you use, but they need a warrant for that. If you use the wrong type of phone, you’re essentially waiving your rights.
David Farquhar is a computer security professional, entrepreneur, and author. He started his career as a part-time computer technician in 1994, worked his way up to system administrator by 1997, and has specialized in vulnerability management since 2013. He invests in real estate on the side and his hobbies include O gauge trains, baseball cards, and retro computers and video games. A University of Missouri graduate, he holds CISSP and Security+ certifications. He lives in St. Louis with his family.