[pandy71]

Originally Posted by orange

there's a nice explanation of pin 16 at wos:
http://www.worldofspectrum.org/forum...12&postcount=8

http://www-user.tu-chemnitz.de/~heha...B-Umschaltung/

Even better but in German - shows real internal life of older TV's - nowadays this is implemented in different way (as signal is sampled in very fast ADC and stored in memory buffer before deinterlacing, resizing and displaying on progressive LCD or PDP display).

Older TV's usually implement RGB switch with 4066 (CMOS QUAD BILATERAL SWITCH). This is why anything higher than Vcc +0.6V can be dangerous, also modern ADC's are usually 3.3V compatible (digital part is powered sometimes lower like 2.5 or 1.8V).