How (Not) secure your mobile phone is.

VK3ELV

VK3ELV

New member
In the 1970-1990s many big companies/hospitals etc. had internal phone systems and only senior management had access to make external or STD/international calls. When you dialed 0 for an outside call a pulse would be sent to tell the system that your phone was barred. If you gave the hangup switch a quick flick after dialing 0, you could call whoever you liked. It was handy for catching up with friends overseas when you were on nightshift.
 
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