Daniel Pitts wrote:> > On 2/28/13 11:22 AM, steve wrote: > > I tested and built the following circuit. > > > > http://www.circuitstoday.com/telephone-in-use-indicator > > > > It all worked fine untill I tried to test it by calling into my phone. > > (the one test I didnt do before I soldered it all together) > > > > What happens is taht the phone rings for a about 1/2 a ring then stops ringing. > > To my surprise when I life the phone up the line is alive eg. Its like the device has answered the phone. > > > > I think that the circuit must be drawing too much power and then telling the phone that it has been answered, because the voltage has gone down. > > > > I have had to replace the Transistors with NTE199, which according to the book are the same. I have also used a rectifier that is a 2 amp 400v SIP 2KBP04M-1. > > Im wondering if I used a different rectifier if that would change the results? > > > > I recognize that your not suppse to take power from the phone co. but I would like to get this circuit working. Can anyone tell me why its not working. > > thanks. > > > > I remember as a teenager, I was playing around with the phone line. I > learned two things. One, if you hook the right resistance across the > line, incoming calls get a "busy" signal, but you can still make > outgoing calls. Two, when someone is calling you, you can get a jolt if > you're holding both ends of the line. > > So, when the phone rings, you get a 60V AC signal. Perhaps you need > slightly more resistance in the line. Unless D2 is already too dim, I'd > try changing R1 to a higher resistance.It was 90 volts.
Phone in use circuit not working
Started by ●February 28, 2013
Reply by ●March 1, 20132013-03-01
Reply by ●March 1, 20132013-03-01
On Fri, 1 Mar 2013, Michael A. Terrell wrote:>> I remember as a teenager, I was playing around with the phone line. I >> learned two things. One, if you hook the right resistance across the >> line, incoming calls get a "busy" signal, but you can still make >> outgoing calls. Two, when someone is calling you, you can get a jolt if >> you're holding both ends of the line. >> >> So, when the phone rings, you get a 60V AC signal. Perhaps you need >> slightly more resistance in the line. Unless D2 is already too dim, I'd >> try changing R1 to a higher resistance. > > It was 90 volts. >Sticking your fingers across a voltage source was never a precise means of measuring voltage. Michael
Reply by ●March 2, 20132013-03-02
On 2013-02-28, steve <stevesemple@lycos.com> wrote:> Thank you for your comments. > > Well I have wired the phone line to the middle pins on the SIP [ + | | - ] > And + to plus and - to Neg of the diagram. > > Thanks for the tips. I will try them. > > By the way one thing. The diagram calls for R2 to be 33k. But a > comment on the bottom says that the value should be the same as R1 > 3.3. So I made R2 3.3. I asumed that the poster was right, because I > know how scematics get screwed up some times. In your opinion should > R2 be 3.3k or 33k. Maybe thats whats wrong? > Regards.33K looks right to me, if perhaps a little too low. the green LED illuminates when the circuit is off-hook which is 40V or more. 33K only gets you ballpark 1.3mA, but much more than that and it'll start looking like off-hook. If you want it to be brighter get a better LED or connect several LEDs in series. -- ⚂⚃ 100% natural
Reply by ●March 2, 20132013-03-02
On Thu, 28 Feb 2013 11:22:00 -0800 (PST), steve <stevesemple@lycos.com> wrote:>I tested and built the following circuit. > >http://www.circuitstoday.com/telephone-in-use-indicator > > It all worked fine untill I tried to test it by calling into > my phone. (the one test I didnt do before I soldered it all > together) > > What happens is taht the phone rings for a about 1/2 a ring > then stops ringing. To my surprise when I life the phone up > the line is alive eg. Its like the device has answered the > phone. > > I think that the circuit must be drawing too much power and > then telling the phone that it has been answered, because > the voltage has gone down. > > I have had to replace the Transistors with NTE199, which > according to the book are the same. I have also used a > rectifier that is a 2 amp 400v SIP 2KBP04M-1. > > Im wondering if I used a different rectifier if that would > change the results? > > I recognize that your not suppse to take power from the > phone co. but I would like to get this circuit working. Can > anyone tell me why its not working. > >thanks.There is quite a long specification for telephone lines in the US. I have a copy, thanks to Don Bowey, when he dropped a copy over at my home back around 2003 or so. It represents an industry composite of various systems and includes envelopes of operation. The gist of it is, as Don wrote before coming over back then, "The FCC R&R require a minimum of 5M of customer premises equipment loop resistance in the on-hook state. Also. at 220uA some Central Offices will declare a line fault and remove the line from service." The basic idea of presenting 5MOhm total customer premises load (that is the TOTAL of all phones and connected equipment) when on-hook is incredibly hard to meet with an unpowered attachment that shows "in use" and "not in use" led lights. I've also read that, "if you are in USA or canada Bellcore specs allow a max of 5micro amps at 48VDC in an on-hook state." That's 10MOhm, in effect, though I believe the 5MOhm for the entire premises still fits the spec. The upshot here is that you aren't going to be seeing an LED lit continuously and still meet on-hook specifications. You can design a system to blink periodically, by drawing very little current onto a capacitor, which charges slowly up and is then discharged into an LED when the voltage rises to the trigger voltage. You can design that to meet specifications. But that's not what you've been given to build. Jon
Reply by ●March 2, 20132013-03-02
"Peabody" <waybackNO746SPAM44@yahoo.com> wrote in message news:20130228-231946.484.0@news.astraweb.com...> steve says... > > > Well I have wired the phone line to the middle pins on > > the SIP [ + | | - ] And + to plus and - to Neg of the > > diagram. > > Yes, I think that's right. > > > By the way one thing. The diagram calls for R2 to be > > 33k. But a comment on the bottom says that the value > > should be the same as R1 3.3. So I made R2 3.3. I asumed > > that the poster was right, because I know how scematics > > get screwed up some times. In your opinion should R2 be > > 3.3k or 33k. Maybe thats whats wrong? > > Well, using 33k will make the circuit draw less current, but > the green LED probably will not light up enough to be > visible. But of course you really don't need the green LED, > just the red one.There are various sources of the specifications that the on/off hook threshold can be looked up, then it should be a few simple calculations to determine the circuit's current draw. Its not uncommon to draw *some* current on hook - many phones maintain a supercap for various memory functions. Assuming an LED doesn't violate the on hook current threshold, maybe a MOSFET (2N7000 etc) could be worked in as its voltage driven rather than needing base current. Its worth bearing in mind; there's usually a zener or two downstream of the bridge rectifier in a phone (typically 12V) - but usually some series resistance as well, so the voltage off hook will settle a little higher.
Reply by ●March 2, 20132013-03-02
Michael Black wrote:> > On Fri, 1 Mar 2013, Michael A. Terrell wrote: > > >> I remember as a teenager, I was playing around with the phone line. I > >> learned two things. One, if you hook the right resistance across the > >> line, incoming calls get a "busy" signal, but you can still make > >> outgoing calls. Two, when someone is calling you, you can get a jolt if > >> you're holding both ends of the line. > >> > >> So, when the phone rings, you get a 60V AC signal. Perhaps you need > >> slightly more resistance in the line. Unless D2 is already too dim, I'd > >> try changing R1 to a higher resistance. > > > > It was 90 volts. > > > Sticking your fingers across a voltage source was never a precise means of > measuring voltage.That's why I bought & built a Heathkit VTVM when I was 13.
Reply by ●March 2, 20132013-03-02
"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in message news:AuSXs.178562$kp4.52700@newsfe09.iad...> Peabody wrote: > >> steve says... >> >> > Well I have wired the phone line to the middle pins on >> > the SIP [ + | | - ] And + to plus and - to Neg of the >> > diagram. >> >> Yes, I think that's right. >> >> > By the way one thing. The diagram calls for R2 to be >> > 33k. But a comment on the bottom says that the value >> > should be the same as R1 3.3. So I made R2 3.3. I asumed >> > that the poster was right, because I know how scematics >> > get screwed up some times. In your opinion should R2 be >> > 3.3k or 33k. Maybe thats whats wrong? >> >> Well, using 33k will make the circuit draw less current, but >> the green LED probably will not light up enough to be >> visible. But of course you really don't need the green LED, >> just the red one. >> >> My concern is that the circuit just draws too much current, >> and therefore shows as off-hook. I would try it at 33k, and >> take the green LED out (or just temporarily jumper across >> it, and see if it works. Beyond that, you could increase >> the resistance of R1, but then that will make the red LED >> dimmer. >> >> There is another version of this circuit that uses MOSFETs >> instead of NPN transistors, and all but the LED resistor are >> in megohms, so it draws very little current when on-hook. >> That's because the MOSFETs switch based on voltage instead >> of current. >> >> http://www.zen22142.zen.co.uk/Circuits/Misc/tiuc.htm >> >> > That one would most likely work better, at least the transistors > are rated at 200V, which is your biggest problem with the first > circuit..Apparently telcos sometimes apply test voltages upto 200V, but the normal operating voltage is considerably lower. 220V MOVs & gas discharge arrestors are commonplace in telecoms equipment, the last phone I stripped & traced had a 200V sidac.
Reply by ●March 2, 20132013-03-02
"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in message news:rpUXs.80033$lC2.51131@newsfe25.iad...> amdx wrote: > >> On 2/28/2013 6:30 PM, Jamie wrote: >> >>> Peabody wrote: >>> >>>> steve says... >>>> >>>> > Well I have wired the phone line to the middle pins on >>>> > the SIP [ + | | - ] And + to plus and - to Neg of the >>>> > diagram. >>>> >>>> Yes, I think that's right. >>>> >>>> > By the way one thing. The diagram calls for R2 to be >>>> > 33k. But a comment on the bottom says that the value >>>> > should be the same as R1 3.3. So I made R2 3.3. I asumed >>>> > that the poster was right, because I know how scematics >>>> > get screwed up some times. In your opinion should R2 be >>>> > 3.3k or 33k. Maybe thats whats wrong? >>>> >>>> Well, using 33k will make the circuit draw less current, but >>>> the green LED probably will not light up enough to be >>>> visible. But of course you really don't need the green LED, >>>> just the red one. >>>> >>>> My concern is that the circuit just draws too much current, >>>> and therefore shows as off-hook. I would try it at 33k, and >>>> take the green LED out (or just temporarily jumper across >>>> it, and see if it works. Beyond that, you could increase >>>> the resistance of R1, but then that will make the red LED >>>> dimmer. >>>> >>>> There is another version of this circuit that uses MOSFETs >>>> instead of NPN transistors, and all but the LED resistor are >>>> in megohms, so it draws very little current when on-hook. >>>> That's because the MOSFETs switch based on voltage instead >>>> of current. >>>> >>>> http://www.zen22142.zen.co.uk/Circuits/Misc/tiuc.htm >>>> >>>> >>> That one would most likely work better, at least the transistors >>> are rated at 200V, which is your biggest problem with the first >>> circuit.. >>> >>> Also this circuit has much less load since it seems to only work >>> when off hook. >>> >>> Jamie >>> >> Here's one I used for years without problem. >> Similar to what Peabody posted, one less FET. >> http://i395.photobucket.com/albums/pp37/Qmavam/PhoneLineInUseIndicator_zpsf78c4525.png I >> can't find the original URL. >> Mikek >> > I remember buying an off hook relay module for a phone line from radio > shaft years ago, back in the old days, it never worked. > > would never switch on. Also, they stopped selling them. Must of been a > reason for it :) > > Some times it is more sensible to buy ready made over making it.With all the discount stores sprouting like weeds, there's many things I once would've built are now cheaper than the parts to buy.
Reply by ●March 2, 20132013-03-02
"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in message news:cORXs.52295$BV7.11863@newsfe24.iad...> steve wrote: >> I tested and built the following circuit. >> >> http://www.circuitstoday.com/telephone-in-use-indicator >> >> It all worked fine untill I tried to test it by calling into my phone. >> (the one test I didnt do before I soldered it all together) >> >> What happens is taht the phone rings for a about 1/2 a ring then stops >> ringing. >> To my surprise when I life the phone up the line is alive eg. Its like >> the device has answered the phone. >> >> I think that the circuit must be drawing too much power and then telling >> the phone that it has been answered, because the voltage has gone down. I >> have had to replace the Transistors with NTE199, which according to the >> book are the same. I have also used a rectifier that is a 2 amp 400v SIP >> 2KBP04M-1. >> Im wondering if I used a different rectifier if that would change the >> results? >> >> I recognize that your not suppse to take power from the phone co. but I >> would like to get this circuit working. Can anyone tell me why its not >> working. >> thanks. > > > I think some one gave you some bad transistor numbers.. > > THe phone system in the US rings at around 100 Volts AC and on hook is > around 50Volts. Off hook may give you around 10 volts and it depends on > how many phones you have at one time off hook. > > The 2N3392 can only handle 25Volts and it may work if you can insure > that the unit will switch on in time to load it down. Further more, the > other transistor will be sitting there with this 50v (on hook), leaking > through the collector. > > The NTE199 replacement isn't much better, it has a 70V limit at best and > most likely will work find when on hook, but when it rings, you can > expect some leaking to be taking place. > > You first need to get HV transistors. > > Try getting some 2N5550 transistors, or the 2N5551 which is a little > higher.. > Mouser.com has 2N5551 for 0.78 ech and they have over 3k in stock.The ones I often find in phones are the MPSA42 & 92 - ones PNP & the other NPN.
Reply by ●March 2, 20132013-03-02
"Jon Kirwan" <jonk@infinitefactors.org> wrote in message news:7sm4j81hs4ep7gti49mukuolcvv68unerc@4ax.com...> On Thu, 28 Feb 2013 11:22:00 -0800 (PST), steve > <stevesemple@lycos.com> wrote: > >>I tested and built the following circuit. >> >>http://www.circuitstoday.com/telephone-in-use-indicator >> >> It all worked fine untill I tried to test it by calling into >> my phone. (the one test I didnt do before I soldered it all >> together) >> >> What happens is taht the phone rings for a about 1/2 a ring >> then stops ringing. To my surprise when I life the phone up >> the line is alive eg. Its like the device has answered the >> phone. >> >> I think that the circuit must be drawing too much power and >> then telling the phone that it has been answered, because >> the voltage has gone down. >> >> I have had to replace the Transistors with NTE199, which >> according to the book are the same. I have also used a >> rectifier that is a 2 amp 400v SIP 2KBP04M-1. >> >> Im wondering if I used a different rectifier if that would >> change the results? >> >> I recognize that your not suppse to take power from the >> phone co. but I would like to get this circuit working. Can >> anyone tell me why its not working. >> >>thanks. > > There is quite a long specification for telephone lines in > the US. I have a copy, thanks to Don Bowey, when he dropped a > copy over at my home back around 2003 or so. It represents an > industry composite of various systems and includes envelopes > of operation. The gist of it is, as Don wrote before coming > over back then, > > "The FCC R&R require a minimum of 5M of customer premises > equipment loop resistance in the on-hook state. Also. > at 220uA some Central Offices will declare a line fault > and remove the line from service." > > The basic idea of presenting 5MOhm total customer premises > load (that is the TOTAL of all phones and connected > equipment) when on-hook is incredibly hard to meet with an > unpowered attachment that shows "in use" and "not in use" led > lights. > > I've also read that, "if you are in USA or canada Bellcore > specs allow a max of 5micro amps at 48VDC in an on-hook > state." That's 10MOhm, in effect, though I believe the 5MOhm > for the entire premises still fits the spec. > > The upshot here is that you aren't going to be seeing an LED > lit continuously and still meet on-hook specifications. You > can design a system to blink periodically,If you can use that 48V to charge a capacitor above 32V without violating the on hook current spec; you can make an LED flash very brightly periodically by dumping the cap into it with a DB3 diac. You'd have to trial & error for how many uF to make the flash bright enough without blowing the LED.
