Abstract: A one-touch dial apparatus and method for registering dialing numbers in a telephone system includes a memory module divided into a plurality of memory blocks, each memory block having a number of memory locations, wherein each of the memory blocks is arranged for each of the corresponding telephones. When an intercom number for a subject telephone is generated from a source telephone, a memory block corresponding to the subject telephone having the intercom number is selected and each of the memory locations in the selected memory block is addressed sequentially. And then, a memory button is assigned to an addressed memory location and a dialing number is registered into the addressed memory location assigned to the memory button.