Editing Phreaking (section)

===Switch hook and tone dialer===
Possibly one of the first phreaking methods was switch-hooking, which allows placing calls from a phone where the rotary dial or keypad has been disabled by a key lock or other means to prevent unauthorized calls from that phone. It is done by rapidly pressing and releasing the switch hook to open and close the subscriber circuit, simulating the pulses generated by the rotary dial. Even most current telephone exchanges support this method, as they need to be [[Backward compatibility|backward compatible]] with old subscriber hardware.<ref>{{cite web|author=SoftCab |url=http://www.modemspy.com/pulse_dialling.modem |archive-url=https://web.archive.org/web/20190323073031/http://www.modemspy.com/pulse_dialling.modem|archive-date=23 March 2019|url-status=dead|title=Phone Call Recorder |publisher=Modemspy.com |access-date=2014-07-24}}</ref>

By rapidly clicking the hook for a variable number of times at roughly 5 to 10 clicks per second, separated by intervals of roughly one second, the caller can dial numbers as if they were using the rotary dial. The pulse counter in the exchange counts the pulses or clicks and interprets them in two possible ways. Depending on continent and country, one click with a following interval can be either "one" or "zero" and subsequent clicks before the interval are additively counted. This renders ten consecutive clicks being either "zero" or "nine", respectively. Some exchanges allow using additional clicks for special controls, but numbers 0-9 now fall in one of these two standards. One special code, "flash", is a very short single click, possible but hard to simulate. Back in the day of rotary dial, technically identical phone sets were marketed in multiple areas of the world, only with plugs matched by country and the dials being bezeled with the local standard numbers.{{citation needed|date=March 2012}}

Such key-locked telephones, if wired to a modern [[DTMF]] capable exchange, can also be exploited by a tone dialer that generates the DTMF tones used by modern keypad units. These signals are now very uniformly standardized worldwide. It is notable that the two methods can be combined: Even if the exchange does not support DTMF, the key lock can be circumvented by switch-hooking, and the tone dialer can be then used to operate automated DTMF controlled services that can not be used with rotary dial.