Yes, it is possible for Comfort to work without a keypad. Comfort can be operated by the home telephone, by pressing * followed by the user code and the # key. Comfort was originally designed as a telephone operated system without keypad.
However, it is not recommended (to do without a keypad) when Comfort is an alarm system. When there is an alarm, the local phones are disconnected so the system is able to dial out. This could cause frustration if someone at home is trying to disarm the system but is unable to access the local phone to do so.