phone tip and ring

[benmin]

are there any adverse affects with not being consistant with how you connect the tip and ring on your phone jacks?

 

[dereckbc]

Depends. If you are talking POTS, then no. In days gone by it would have mattered as the keypads were polarity sensitve, and some signalling took place, but not anymore. However it is just good practice to keep it straight.

 

[LarryFine]

In case anyone ever wondered where the terms 'tip' and 'ring' came from, look at a stereo headphone plug. Notice the three contacts: the 'tip', the 'ring', and the sleeve, or main shank. A mono plug does not have the 'ring' contact.

Now, think back to the olden days of the manual switchboard and operators. The plugs the operator used were the forerunners of the modern 1/4" 'phone plug', although the old plugs had a slighly larger diameter and longer tip.

The tip was the 'hot' wire, the ring was referred to as HRG (High Resistance to Ground), and the sleeve was ground, but not part of the phone circuit.

 

[GMc]

Very interesting Larry, Thanks

GMc

 

[cosmos]

Just like power wiring, be consistant with color coding

Just like power wiring, be consistant with color coding

I have had problems when I interchange the ring/tip connection. Anyone know the voltage/current/frequency of todays telephone circuits?

 

[zbang]

POTS lines are nominally 48vdc positive ground (actually about 54v). I can't recall the current spec specifically; IIRC you need at least 10ma to operate the line. Current is limited by the line length and wire guage, which can be a mix of 19g, 24g and 26g, and over 20,000'. For very long lines, the telco may increase the supply voltage to get the required current.

Ringing is generally 90vac 20Hz (nominal) superimposed on the 48vdc.

As mentioned, most modern equipment is not polarity sensitive, but there's a lot of old phone gear out there.

 

[LarryFine]

Years ago, when I was in high school, the electronics club took a tour of the local central office, and this is where I learned a lot of this stuff. If some has been modernized, forgive me.

The phone equipment actually runs on a large bank of batteries, which are recharged when the voltage hits 48, and stops charging at 52v. They have a standby benerator for power outages.

I also remember the ring voltage as 90, but at 25Hz, and a square wave, but I'll concede to Z's memory, as it was 30+ years ago. Interestingly, pulse-dialing phones still function on modern systems.

 

[dereckbc]

I have had problems when I interchange the ring/tip connection. Anyone know the voltage/current/frequency of todays telephone circuits?

I can tell you exactly what it is.

Voltage is between 52 and 54 volts DC when the phone is on the hook and 48 VDC nominal.

Current at your home if T&R are shorted cannot be defined because of the unknown cable resistance. However it is limited to 60-milli-amps at the CO, and anything less than 5-milliamps at your home your equipment will not work. So the anwer is less than 60 ma and greatet than 5 ma.

Ring voltages vary but the standard is 105 VAC set by Western Electric (now known as Lucent) some years ago. The frequency depends on if you are on a party line or not. Standard is 20 Hz but for party lines you can have 20, 25, 30,,, 50.

 

[TysonLV]

Yes, tip and ring does matter if you are going to connect a digital phone system such as Nortel Norstar, NEC, etc. The phonesets are polarity sensitive.

 

[hbiss]

Yes, tip and ring does matter if you are going to connect a digital phone system such as Nortel Norstar, NEC, etc. The phonesets are polarity sensitive.

I don't think so for the reason that a line cord itself will transpose tip and ring as will modular adapters and couplers.

That's not to say that you shouldn't wire your jacks properly any more than you should not pay attention to the hot and neutral on a receptacle. Polarity is not usually a problem with telephones.

-Hal

 

[mkoloj]

I agree with Hal, after I read the 2 posts above me I just took and reversed polarity on the Nortel Meridian digital phone (M3904) that is on my desk and it worked perfectly either way the pair was punched down. So it does work but it doesn't make it right, nor does it mean that the phone will not be replaced with something that is polarity sensitive one day, so I wouldn't go around arbitrarily making connections to phone jacks.
I remember about 10 years ago I had a phone in my bedroom and the keypad never worked. One day we had trouble with the line and a telco tech came out to the house and after he fixed the line problem we had I mentioned the other problem with the keypad in my room and he opened the jack and did something to the wiring, that I will assume was correcting a polarity mistake that a young Mkoloj made when he installed the jack. Keypad worked fine after that.

 

[dereckbc]

I remember about 10 years ago I had a phone in my bedroom and the keypad never worked. One day we had trouble with the line and a telco tech came out to the house and after he fixed the line problem we had I mentioned the other problem with the keypad in my room and he opened the jack and did something to the wiring,

That is b/c the old 2500 type keypads were polarity sensitive. Now days just about any phone worth owning have diode bridges to accept either polarity.

Here is a good example some might recall. Remember going to a pay phone, pick up the reciever, heard dial tone, but the keypad would not work untill you plugged it with a coin? Well polarity is how the TELCO used to operate the pay phone. Once yu plugged in the coins, the switch at the CO reversed the polarity and enabled the keypad so you could dial and break dialtone. Heck if you go to some some rural towns, you can still find those things.

 

[leecordochorea]

Some fax machines are polarity sensitive.