Amplified Phones
Clarity DECT 6.0 Cordless Amplified phone
This phone will amplify conversations and block out background noise. Compatible with hearing aids and amplifies up to 30 decibels for the hearing impaired. This phone caters to people who suffer from hearing loss or impairment.
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Picture Care Amplified Phone
The picture care phone amplifies conversation up to 30 decibels. It also allows you to store up to ten contacts along with their picture so that numbers are easily accessible. This product is perfect for the hearing impaired, have trouble remembering numbers or names, or suffer from memory loss.
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Amplicom AB900 Standalone Amplified Answering Machine
This answering machine will amplify your messages and allows you to adjust the speed and tone of messages so that they are easier to understand. Ideal for those who are hearing impaired or have learning disablities.
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Pricing
These amplified phones can be purchased at a price ranging from $40 to over $1000 at any store or websites that specifically sells to people with impairments or disabilities such as enablemart.com . You can also choose a plan from any major cell phone carrier such as Verizon or Sprint.

I think that the Clarity DECT 6.0 Cordless Amplified phone is the best choice because of its price and simplicity.