How has Section 3653 of the Criminal Code been interpreted in the context of revocation of probation?

The portion of section 3653 pertinent to this case reflects the distinction made in section 3651 between suspending "the imposition" of sentence and suspending its "execution." When the "imposition" is suspended no sentence exists until one is imposed. Therefore, upon revocation of probation where "imposition" of sentence was suspended, the sentencing court is free to impose any sentence it originally might have imposed. Roberts v. United States, supra, 320 U.S. at 271, 64 S.Ct. 113. Suspension of the "execution" works differently. Upon revocation of probation the suspension is lifted and the original sentence goes into effect unless a lesser one is imposed.