Tip and ring - wikipedia Tip and ring Jump to : navigation , search 1 : Sleeve , 2 : Ring , 3 : Tip , 4 : Insulators Tip and ring are the names of the two conductors or sides of a telephone line . The terms originate in reference to the telephone plugs used for connecting telephone calls in manual switchboards . One side of the line is connected to the metal tip of the plug , and the second is connected to a metal ring behind the tip , separated and insulated from the tip by a non-conducting material . When inserted into a jack , the plug 's tip conductor connects first , followed by the ring conductor . In many European countries tip and ring are referred to as the A and B wires . Neither of the tip and ring conductors is permanently connected to earth ground , but may be connected to ground during signaling operations . Typically , the ring conductor has a direct current ( DC ) potential of − 48 V to − 52 V with respect to the tip conductor when the line is in the on - hook ( idle ) state . Floating both conductors , not referencing either one to ground , minimizes the pickup of hum from any nearby alternating current ( AC ) power wires . Contents ( hide ) 1 Origin 2 Line voltage 3 Polarity 4 Color code 5 References 6 External links Origin ( edit ) The terms tip and ring originated in the early days of telephony when telephone operators used plugs to connect customer calls . They are named after the parts of the plug to which the wires were connected . The words are often abbreviated as T and R . Line voltage ( edit ) The telephone company maintains large battery systems that supply DC line voltage for the operation of analog telephone service at customer locations . The voltage supplied is a compromise between operational needs for reliable service and safety precautions for customers and service personnel . The length of the line to a customer telephone interface presents a resistance across which the central office voltage experiences a drop and therefore the voltage at the customer site may vary . The nominal battery ( system ) voltage is 52.1 V , based on a 24 - cell lead - acid battery . The voltage at a subscriber 's network interface is typically 48 V between the ring and tip wires . In the middle 20th century , long loops in many rural areas of North America used range extenders , which operated at 100 or 130 volts to ensure reliable signaling . Some rural switching systems were designed to apply range extenders internally and thus share a few extenders among many lines , while for other lines , one extender was applied externally per line . To ring the telephone to alert a subscriber to an incoming call , the central office superimposes a 20 Hz AC signal , at a nominal voltage of 105 volts , over the DC voltage present on the idle line . Historically several multi-frequency systems have been used , however , for selective alerting of multiple subscribers connected to a party line , for which the A.C. voltage may be as high as 150 V . Polarity ( edit ) To provide cathodic protection against corrosion of line wires , operating potential of telephone lines is typically negative with respect to ground , and the tip side is generally close to the ground potential . Thus , all power supplies for telecommunication equipment are designated to supply a negative voltage . In the early years of the telephone industry when rotary dial instruments were in use , the polarity when connecting a telephone set to the tip and ring wires was usually important only for properly ringing a telephone , especially in party line service with selective ringing , and for correctly identifying the calling customer on certain party lines for toll calls . When Touch - Tone service was introduced in the 1960s , the dual - tone multi-frequency signaling ( DTMF ) tone generator also required correct polarity as it depended on the line D.C. voltage for operation . Later Touch - Tone telephones included a diode bridge that eliminated the polarity sensitivity , so that consumer telephone service is essentially immune to reversal today . However , some special circuits , such as some direct inward dialing ( DID ) trunks , T - 1 lines , and ground start lines connected to field side ( terminal ) equipment , e.g. , a corporate private branch exchange ( PBX ) switch , correctly operate only with proper tip and ring polarity . Color code ( edit ) When simple on - premises wiring is color - coded , two - wire telephone plugs or the first pair of a multi-pair connector commonly have the tip wire coded green and ring coded red . In four wire plugs , the second pair has black tip and yellow ring . A third pair consists of white tip and blue ring . For larger cable assemblies more complex schemes such as the 25 - pair color code are used . Some telephone technicians used various phrase , such as red - right - ring - rear , or ring - right - red - rough , to remember that the red wire connects to the right - side post in the wall jack and to the ring on the plug and to the rear lug on main distribution frames . Sometimes rough or ridge was added for jumper wires with a tactile code . References ( edit ) Jump up ^ W.D. Reeve , Subscriber Loop Signaling and Transmission Handbook -- Analog , IEEE Press ( 1992 ) , ISBN 0 - 87942 - 274 - 2 , p. 138 . Jump up ^ W.D. Reeve , Subscriber Loop Signaling and Transmission Handbook -- Analog , IEEE Press ( 1992 ) , ISBN 0 - 87942 - 274 - 2 , p. 39 . External links ( edit ) How to Wire a Phone Jack Basics of Telephone Wiring Telephony Basic Information and Terms Retrieved from `` https://en.wikipedia.org/w/index.php?title=Tip_and_ring&oldid=807186914 '' Categories : Telephony equipment Hidden categories : All articles with unsourced statements Articles with unsourced statements from June 2015 Talk Contents About Wikipedia Add links This page was last edited on 26 October 2017 , at 13 : 18 . Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply . 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what is the idle line voltage in australia
Tip and ring are the names of the two conductors or sides of a telephone line . The terms originate in reference to the telephone plugs used for connecting telephone calls in manual switchboards . One side of the line is connected to the metal tip of the plug , and the second is connected to a metal ring behind the tip , separated and insulated from the tip by a non-conducting material . When inserted into a jack , the plug 's tip conductor connects first , followed by the ring conductor . In many European countries tip and ring are referred to as the A and B wires . Neither of the tip and ring conductors is permanently connected to earth ground , but may be connected to ground during signaling operations . Typically , the ring conductor has a direct current ( DC ) potential of − 48 V to − 52 V with respect to the tip conductor when the line is in the on - hook ( idle ) state . Floating both conductors , not referencing either one to ground , minimizes the pickup of hum from any nearby alternating current ( AC ) power wires . The terms tip and ring originated in the early days of telephony when telephone operators used plugs to connect customer calls . They are named after the parts of the plug to which the wires were connected . The words are often abbreviated as T and R . The telephone company maintains large battery systems that supply DC line voltage for the operation of analog telephone service at customer locations . The voltage supplied is a compromise between operational needs for reliable service and safety precautions for customers and service personnel . The length of the line to a customer telephone interface presents a resistance across which the central office voltage experiences a drop and therefore the voltage at the customer site may vary . The nominal battery ( system ) voltage is 52.1 V , based on a 24 - cell lead - acid battery . The voltage at a subscriber 's network interface is typically 48 V between the ring and tip wires . In the middle 20th century , long loops in many rural areas of North America used range extenders , which operated at 100 or 130 volts to ensure reliable signaling . Some rural switching systems were designed to apply range extenders internally and thus share a few extenders among many lines , while for other lines , one extender was applied externally per line . To ring the telephone to alert a subscriber to an incoming call , the central office superimposes a 20 Hz AC signal , at a nominal voltage of 105 volts , over the DC voltage present on the idle line . Historically several multi-frequency systems have been used , however , for selective alerting of multiple subscribers connected to a party line , for which the A.C. voltage may be as high as 150 V . To provide cathodic protection against corrosion of line wires , operating potential of telephone lines is typically negative with respect to ground , and the tip side is generally close to the ground potential . Thus , all power supplies for telecommunication equipment are designated to supply a negative voltage . In the early years of the telephone industry when rotary dial instruments were in use , the polarity when connecting a telephone set to the tip and ring wires was usually important only for properly ringing a telephone , especially in party line service with selective ringing , and for correctly identifying the calling customer on certain party lines for toll calls . When Touch - Tone service was introduced in the 1960s , the dual - tone multi-frequency signaling ( DTMF ) tone generator also required correct polarity as it depended on the line D.C. voltage for operation . Later Touch - Tone telephones included a diode bridge that eliminated the polarity sensitivity , so that consumer telephone service is essentially immune to reversal today . However , some special circuits , such as some direct inward dialing ( DID ) trunks , T - 1 lines , and ground start lines connected to field side ( terminal ) equipment , e.g. , a corporate private branch exchange ( PBX ) switch , correctly operate only with proper tip and ring polarity . When simple on - premises wiring is color - coded , two - wire telephone plugs or the first pair of a multi-pair connector commonly have the tip wire coded green and ring coded red . In four wire plugs , the second pair has black tip and yellow ring . A third pair consists of white tip and blue ring . For larger cable assemblies more complex schemes such as the 25 - pair color code are used . Some telephone technicians used various phrase , such as red - right - ring - rear , or ring - right - red - rough , to remember that the red wire connects to the right - side post in the wall jack and to the ring on the plug and to the rear lug on main distribution frames . Sometimes rough or ridge was added for jumper wires with a tactile code .
a direct current (DC) potential of −48V to −52V with respect to the tip conductor