Abstract: An automatic release device for automatically releasing hold-on setting of an outside line call wherein a first telephone when having an outside line call from a second telephone and set to the hold-on state can be released from the hold-on setting by use of a sensing means detecting signals based on the hook-down at the second telephone slde. Further a transfer method for an outside line call, by using a conference call system served by Telegraph and Telephone Corporations wherein a running outside line call received from a second telephone by a first telephone through outside line wire is set to enable the conference call and the first telephone is set to the hold-on state so as to allow persons at the second and third telephones to talk with each other, wherein a sensing means for detecting signals based on hook-down of either of the second and third telephones is used to release the first telephone from the hold-on state.