the spotting table needs to either descend part-way to handle standing pins after the first ball, or to fully descend (once loaded from the pin-turret above it) to set the new rack of pins for the next frame. The Model A, A-2 and JetBack series pinsetters all characteristically halt their operation, should the pin turret not yet be full of pins for the next frame, by pausing the sweep bar at the back of its rearwards travel and holding the table in its fully elevated position, until the pin-turret fills and releases its load into the spotting table's upper level. This style of machine is typically loaded with 20 pins, though most proprietors normally put in 21 pins to facilitate quicker loading and faster operation of the pinsetter, especially in cases where the bowler(s) make two strikes in quick succession — on all the Model A-based unit designs, the "second ball cycle" used for both a second ball's delivery or a strike won't complete if the turret is not full, with the deck waiting in its elevated position as stated previously. Adding an extra pin does not put undue stress on the machine, but adding more than that is not advisable due to damage that can occur to the machine. Other centers will only load the pinsetter with 19 pins. Having only 19 pins in the machine will cause fewer stops from time to time but it will slow down the progress of the game if multiple strikes are thrown in succession. The later A2 and JetBack versions, otherwise each virtually identical to the original Model A design, were augmented enough to have much faster ball return action than the original Model A units. the A-2 was also designed to be a faster machine overall to increase the number of frames that could be bowled in a given time frame, thus increasing the revenue of the bowling center. The visible deck shield, as well as the noticeable sounds of pins entering the pin elevator (sounding like bowling pins rattling in a metal drum) and of the next set of pins dropping from the turret into the deck chutes, are unique to the Brunswick A series. There is a large Brunswick "crowned-B" (their 1950s logo) on the front of the deck shield of the Model A, "A-2" on the A-2 deck shield front, and "JetBack" on the JetBack deck shield front,