Frequently Asked Questions

Digital Spread Spectrum (DSS) Cordless Telephone Technology

Conexant introduced the industry’s first complete 900MHz DSS cordless telephone chipset in late 1995. Today, Conexant is the industry’s market leader. To support the emerging market for 2.4GHz cordless phones, Conexant debuted its solution for 2.4GHz handsets in September 1999. Conexant’s solutions deliver unmatched flexibility for OEMs supporting both 900MHz and 2.4GHz cordless designs.

What is Digital Spread Spectrum technology?
Digital Spread Spectrum is a digital cordless telephone technology. It looks and feels like the cordless phones many people use in their homes today. However, DSS provides the longest range, best sound quality and highest security available in a cordless phone. For example, DSS allows users to continue their telephone conversations while they are as much as a mile away from the phone’s base station. So, you can walk to the end of the driveway to pick up your mail, or visit your neighbor’s house, without missing a call.

How big is the cordless phone market? How widely used are DSS phones today?
Conexant is the currently the leading supplier of semiconductor solutions for DSS cordless phones. According to industry analyst firm Dataquest, the semiconductor market for digital cordless handsets will grow to just below $1.4 billion in 2003, with unit sales of DSS cordless phones reaching more than 37 million units by 2003

What are Conexant’s DSS product offerings?
Conexant offers every phone manufacturer the opportunity to design a full line of either 900MHz or 2.4 GHz DSS cordless, which include Caller ID, 2-line, speakerphone, and/or answering machine (TAD) support.

What customers use Conexant’s DSS solutions?
AT&T, CIDCO, GE, Sanyo, Sony, Uniden, and VTech have incorporated Conexant solutions into their DSS cordless phones.

Specifically, what is unique about Conexant’s DSS solutions?
First, Conexant’s DSS solutions are proven, having provided the longest range and clearest audio for over 6 years. Second, Conexant’s solutions provide superior flexibility and fast time-to-market for cordless phone manufacturers. OEMs can quickly and easily deliver products based on Conexant’s solutions because all of the baseband technology is shared between 900MHz and 2.4GHz designs. Furthermore, by using Conexant’s new API architecture, phone manufacturers can easily customize their firmware. Other features exclusive to Conexant’s offering include Smart Channel Hopping™, which automatically scans the frequency band for the best channel; Smart Power Management™ for extended battery life; unparalleled protection from outside “eavesdropping”; and simultaneous data and voice channels for seamless transfer of information to the handset, which maintains clear audio.

How does “spread spectrum” work?
The term “spread spectrum” means just that — the voice data is literally “spread” over a wide spectrum, unlike with non-spread spectrum phones, which use only a narrow spectrum for communication. Spread spectrum is a modulation technique originally developed for military applications as a secure means of communication unencumbered by hostile attempts to disrupt it. The spread spectrum signal is uniformly spread over a wide range of frequencies for transmission, allowing the signal to avoid or eliminate disruption in today’s residential airspace, which includes baby monitors, microwave ovens, garage door openers, and other cordless phones. During operation, Conexant’s DSS solution continuously and automatically scans the frequency band for the best channel. If another device tries to use the same frequency, the phone performs a Smart Channel Hop™ to an available clear channel and conversations are uninterrupted. In addition, the receiving phone contains a pre-assigned, de-spreading code which undesired signals do not have, so the noise gets filtered out and users enjoy crystal clear sound quality.

I’ve heard that DSS cordless phones have greater range than other cordless phones. How is that possible?
The FCC allows spread spectrum phones to transmit up to 1 watt of power — 1,000 times greater than other types of cordless phones which are limited to 1 milliwatt. This allows spread spectrum phone signals to penetrate walls easily and cover greater distances to provide longer range and better clarity.

How does the range of a DSS cordless phone compare to other cordless telephone technologies?
DSS cordless phones provide a range seven to eight times that of an old 25-channel analog cordless phone, or three to four times the range of a non-spread-spectrum analog or digital telephone. OEM customers currently have phones in production with ranges up to one mile.

What’s the difference between DSS and 46/49 MHz (25-channel) cordless phones?
The obvious difference is that 46/49MHz cordless phones are analog. The majority of 46/49 MHz cordless phones in use today feature 25 channels. These phones use the same basic technology as the previous 10-channel models, which have neither built-in protection from interference nor any enhanced range capability. The voice quality has not been improved and no provisions have been included for greater security.

In contrast, DSS phones efficiently filter out unwanted noise, and with spread spectrum modulation, the transmitted signal is spread out over a very large bandwidth to avoid areas of interference. As a result, DSS phones provide clearer sound quality, a much longer range, the ultimate in privacy, and no cross talk.

What about 900MHz analog cordless phones? How do they improve upon the early analog technology?
900MHz analog cordless phones were developed utilizing the 902-928 MHz part of the spectrum to overcome the inherent overcrowding problems experienced by 46/49 MHz phones. The 902-928 MHz band is characterized by shorter wavelengths that travel more effectively. The wavelength of a 46/49 MHz phone is 18 feet, while the wavelength of a 900MHz transmission is only one foot. The shorter 900MHz transmission bounces off objects more efficiently and in typical residential environments, travels a greater distance than the 46/49 MHz signal. It was expected that the higher frequency phones would provide noise-free sound quality and a greater range, but customer expectations were not met. The reason for continued interference is that the analog 900MHz phones use the same analog technology as the 46/49 MHz phones. Unfortunately, the security and sound quality limitations of analog technology cannot be overcome simply by using a different frequency band.

How do digital cordless phones differ from the earlier analog models?
Digital cordless phones use internal circuits that can provide markedly better sound quality and security than analog solutions. The user’s analog voice is digitally encrypted before being transmitted to the base station and is scrambled in such a way that only the base station can decipher it. In addition, a digital security code can be transmitted each time the phone is used. However, digital phones are not allowed to send any more power than an analog phone, and ultimately suffer similar range limitations.

How do DSS phones compare to 900MHz analog or 900MHz digital cordless phones?
Conexant’s DSS solutions build upon the increased security offered by digital technology, while significantly improving upon the clarity and range. Spread spectrum technology sends multiple copies of the voice signal, so that even if some of the information is corrupted, the voice signal can still be perfectly reconstructed for even clearer voice quality. Furthermore, DSS allows transmission with up to 1 watt of power, extending the range of the telephone significantly. Finally, Conexant’s DSS technology provides superior security, since only the receiver has a copy of the pre-assigned spreading code. Plus, the scrambling code changes every eight or 10 times the phone is parked, and there are more than 16 million codes. As a result, interception is nearly impossible.

What are the differences between 900MHz and 2.4GHz spread spectrum phones?
In many ways, 900MHz and 2.4GHz phones are very similar. The primary difference between them is that 900MHz and 2.4GHz phones operate in different frequency bands. Plus, 2.4GHz phones offer 40 channels, or twice as many as 900MHz phones. Also, 2.4GHz DSS phones can be deployed throughout the world.

What are Type I and Type II Caller ID and how do they differ?
Type I and Type II Caller ID are value-added services offered by your local telephone company. Type I Caller ID is when you receive the caller’s name and phone number between the first and second rings on a new telephone call to your house. While on that call, Type II Caller ID provides you with the second caller’s name and number just after you receive a call-waiting tone. Once your telephone receives this information, it must respond back to the Telephone Company for confirmation.

Does Conexant’s offering support voice messaging?
Local phone companies offer voicemail as a value-added feature. To indicate that a message is waiting, a stuttering dial tone can be heard. Until now, there was no visible way of learning that a message was waiting. Fortunately today, Conexant’s chipset can detect this stuttering tone and--when you have voicemail in your central-office mailbox--issue a signal to a message waiting indicator light.