| A cordless telephone is an electronic telephone that | | | | best of the cordless telephones fail to match the audio |
| comprises of a wireless handset and a base unit. | | | | quality that a high quality phone wired to a good |
| Communication is carried out between the handset | | | | telephone line provides. |
| and the base using radio waves. The wireless handset | | | | Sidetone (echo of voice heard in the speaker of the |
| can be operated only within a fixed range from its | | | | receiver), disturbing constant background noise that is |
| base unit. The range of operation is generally within 100 | | | | due to the cordless system, and inability to obtain a full |
| meters. The base unit needs electricity to power it. | | | | frequency response that is available in a wired phone |
| Batteries are used to power the cordless handset. | | | | are few of the reasons for a not-so-good audio |
| Placing the cordless handset in the cradle in the base | | | | quality. Rare exceptions, obviously, always exist that |
| unit recharges these batteries. A period of 12 to 24 | | | | sound unbelievably similar to a wired telephone. But |
| hours is required for recharging the batteries. | | | | even these are considered as `fluke` by most industry |
| With features like cell handover, data transfer and | | | | standards. |
| international roaming (on a limited scale), the once | | | | Higher frequency is now being used in other home |
| clear-cut line between mobile telephones and cordless | | | | products like the microwave oven, Baby monitor, |
| telephones has now been blended by the modern | | | | Bluetooth, wireless LAN, etc. Thus, cordless telephones |
| cordless telephone standards. | | | | using higher frequency may face interference from |
| Frequency bands have been assigned in each country | | | | signals from these devices. |
| for cordless telephones. Advertisements by | | | | Eavesdropping is a constant security threat for analog |
| manufacturers claiming that there is an improvement in | | | | telephones. Any one with a radio scanner and within |
| audio range and quality with higher frequency are a | | | | range can pick up these signals and listen to |
| common sight. But that is not the case. Actually, higher | | | | conversations. Modern digital technology is thus being |
| frequencies have been seen to exhibit worse | | | | used to take care of this kind of unauthorized access. |
| propagation in ideal case. There is also a tendency for | | | | DSS (Digital Spread Spectrum) makes use of |
| the path loss to increase with higher frequencies. | | | | frequency hopping, i.e. spreading up of audio signal |
| Locally varying factors such as antenna quality, signal | | | | over a wider range in a pseudorandom fashion. DSS |
| strength, the modulation method being used and | | | | signal sounds like noise bursts to a radio scanner or |
| interference are more influential than other factors. | | | | any other analog receiver. This signal makes sense |
| With Landline telephones working on a bandwidth of | | | | only to that base unit which has the same |
| about 3.6 kHz (a small fraction of the frequency that a | | | | pseudorandom number generator as the cordless |
| human ear can interpret), the transfer of audio is | | | | handset. Each time the cordless handset is returned to |
| carried out with an audio quality that is just enough for | | | | its cradle, a new unique generator is chosen from |
| the parties to communicate each other. Because of | | | | thousands of options. |
| this limitation in the design of the phone system itself, it | | | | DSS generates a signal spread that leads to a kind of |
| is not possible to improve the audio quality beyond a | | | | redundancy, which gives rise to increased |
| particular limit in cordless telephones. | | | | signal-to-noise ratio. It also leads to increase in signal |
| Most of the good-quality cordless telephones try | | | | range and decreases interference susceptibility. It is |
| transferring the audio signal with lowest possible | | | | easier to use this kind of wide-bandwidth security |
| interference and greatest possible range. Even the | | | | option with higher frequency. |