This instrument is designed specifically as hot-line or answer-only.
Provided that these telephones are used behind a switch offering hot-line facilities, they make an ideal alternative to using ordinary telephones for this role.
Being brightly coloured they are easy to see if positioned in strategic locations. Such places, by definition, are usually in public areas. With no keypad to make them "attractive", the phones are less likely to disappear from these areas.
An alternative use for the telephone is to provide an answer-only service. Again, this facility is normally provided in public areas. The colour of the phone helps to make it stand out and the lack of a keypad deters people from stealing the phone.
Taken from Interquartz marketing material
Last revised: October 26, 2021