Context : The observed distribution of orbital periods of Algols with a B-type primary at birth agrees fairly well with the prediction from conservative theory .
Conservative evolution fails , however , to produce the rather large fraction of Algols observed with a high mass-ratio , especially : q \in [ 0.4-0.6 ] .

Aims : In order to keep Algols for a longer time with a higher mass-ratio without disturbing the distribution of orbital periods too much , interacting binaries have to lose a significant fraction of their total mass without losing much angular momentum before or during Algolism .
We propose a mechanism that meets both requirements .

Methods : In the case of direct impact the gainer spins up : sometimes up to critical velocity .
Equatorial material on the gainer is therefore less bound .
A similar statement applies to material located at the edge of an accretion disc .
The incoming material moreover creates a hot spot in the area of impact .
The sum of the rotational and radiative energy of hot spot material depends on the mass-transfer-rate .
The sum of both energies overcomes the binding energy at a well defined critical value of the mass-transfer-rate .
As long as the transfer-rate is smaller than this critical value RLOF happens conservatively .
But as soon as the critical rate is exceeded the gainer will acquire no more than the critical value and RLOF runs into a liberal era .

Results : Low-mass binaries never achieve mass-transfer-rates larger than the critical value .
Intermediate-mass binaries evolve mainly conservatively but mass will be blown away from the system during the short era of rapid mass-transfer soon after the onset of RLOF .
We have calculated the evolution of binaries with a 9 M _ { \odot } primary and a 5.4 M _ { \odot } companion over a range of initial orbital periods , covering case-A RLOF .
Mass-loss from the system is achieved during direct impact only .

Conclusions : We find systems that show Algolism for more than ten million years .
RLOF occurs almost always conservatively .
Only during some 20,000 years the gainer is not capable of grasping all the material that comes from the donor .
The mass-ratio q \in [ 0.4-0.6 ] which was hardly populated by conservative evolution now contains Algols for a significant fraction of their existence .