Threshold switches delay time

Fig. 6.2. Sketch of the time response to a voltage pulse Vp > and to interrogating voltage pulses V < for (a) a threshold switch and (b) a memory switch. Switching from OFF to ON occurs after a delay time tj. The memory is SET after a lock-on time interval LO after switching. The threshold switch (a) returns to OFF after the end of the Vp pulse. The memory switch (b) requires a RESET current pulse to return to the high resistance OFF state.

Delay Due to Resistive Losses. On electrically long, lossy lines, the signal rise time is degraded by dispersion in the interconnection. Dispersion delays and attenuates the high-frequency components of the signal more than the low-frequency components because of the frequency-depen-dent resistance of the interconnection. The rise time degradation contributes additional delay before the switching threshold is reached at the end of the line. 

The model thus shows how thresholds in the phosphorylation-dephosphorylation cascade controlling cdc2 kinase play a primary role in the mechanism of mitotic oscillations. The model further shows how these thresholds are necessarily associated with time delays whose role in the onset of periodic behaviour is no less important. The first delay indeed originates from the slow accumulation of cyclin up to the threshold value C beyond which the fraction of active cdc2 kinase abruptly increases up to a value close to unity. The second delay comes from the time required for M to reach the threshold M beyond which the cyclin protease is switched on. Moreover, the transitions in M and X do not occur instantaneously once C and M reach the threshold values predicted by the steady-state curves the time lag in each of the two modification processes contributes to the delay that separates the rise in C from the increase in Af, and the latter increase from the rise in X. The fact that the cyclin protease is not directly inactivated when the level of cyclin drops below C prolongs the phase of cyclin degradation, with the consequence that M and X will both become inactivated to a further degree as C drops well below C. ... 

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