Actually, what I want (need) to do is generate this voltages to activate a telephone without hooking it to a line. This is for testing purposes. Calvin -----Original Message----- From: Ron Fial To: PICLIST@MITVMA.MIT.EDU Date: Jueves 9 de Julio de 1998 9:34 PM Subject: Re: [OT] POTS specifications??? >To get you started, The open circuit voltage is 48 volts (called on hook), and the off-hook voltage is about 6 to 15 volts, depending on the telephone used. A typical 600 Ohm phone should yield about 12 volts when off hook. The ring voltage is about 90 volts AC, the frequency can vary depending on the system (The different frequencies used to be used to select different phones on a party line). The caller ID information is sent between the first and second rings as an fsk modulated modem signal at 1200 baud, as i recall. The dial tone is made up of two very accurate sine waves mixed together, so its sounds the same everywhere and is easy to detect electronically. > >You are not supposed to hook un-registered devices to the phone line (FCC regulates this). Most phone interface circuits isolate the line with a 600 to 600 ohm transformer, go off hook with a relay contact, and optically isolate the ring detection, so that no DC connection exists between the line and the customer equipment. Be careful not to accidentally connect the phone line to a power supply or AC. This could be vry very expensive for you. > > Regards, > Ron Fial >=================================================================== >At 07:45 PM 7/9/98 -0600, you wrote: >>Sorry to bother you again with another OT. >> >>Does anybody know a link where I can find info on the US telephone system >>specifications? >> >>Actually, what I need to know is the voltajes that must be present on the >>lines, and the signal levels. >> >>Calvin >> >