The vibrating pad alarms are particularly useful for deaf-blind people.
Why, only a little while ago people thought it quite impossible to teach the deaf-blind anything; but no sooner was it proved possible than hundreds of kind, sympathetic hearts were fired with the desire to help them, and now we see how many of those poor, unfortunate persons are being taught to see the beauty and reality of life.
As to the two-handed alphabet, I think it is much easier for those who have sight than the manual alphabet; for most of the letters look like the large capitals in books; but I think when it comes to teaching a deaf-blind person to spell, the manual alphabet is much more convenient, and less conspicuous....
Well, I must confess, I do not like the sign-language, and I do not think it would be of much use to the deaf-blind.
Most blind people are aided by the sense of sound, so that a fair comparison is hard to make, except with other deaf-blind persons.