Hi Chris,

It's not so easy to interpret the graphs 26 and 27 the correct way. The shaded area in 26 actually consists of horizontal lines, the value of which are sampled when the memory gate conducts. In 27 something similar for the rest period between end of hold-off and next trigger event.
When probe TP555 at a slow sweep speed, 5 ms/div, trigger from this signal and play with the SCAN rate of the 7T11, you can get a more or less stable display. You will recognize the 7T11 sweep as a rising envelope with an amplitude of 5 V. The output at TP564 is a nice 2X inverted, down going sweep signal with amplitude 10 V. TP556 shows about the same as TP564 but with small amplitude.

Albert