Dial 9 Telephone Service

The telephone company offered me a big discount if I agreed to service that requires me to dial “9” before every call. Of course I accepted, but it seems odd to me that in the computer age, there’s some benefit to making people do this. In other words, why can’t it be done automatically by the phone company? Why can’t they set up their computer system to treat every call I make as if I’d dialed “9” before placing the call?

If you don’t dial nine, then your local phone switch can handle the call, without tying up any phone company equipment, right?.

Usefull, I assume, for large facilities that do a lot of internal phone chatting.

Are you talking about a business service, or residential? VOIP?

The only reason you’d normally have to dial 9 for is to get an outside line, i.e one that isn’t part of a PBX. If you don’t have your own personal switchboard, there should be no reason to dial 9. It sounds quite unusual.

Did they offer this to you for your business with a bunch of employees, or for residential service? I’ve never heard of it for residential service. For a business, it allows internal calls to be handled without ever reaching the local office switch.

This reminds me, what happened to all the 10-10 dialing schemes? I haven’t heard about any of those in years.

Free or low cost long distance offered by local telephone and cell phone companies is the reason. I haven’t paid for a long distance call in years.

Carrier Access Codes are still around. (Although to be accurate they’re really 101-XXXX codes, which replaced the earlier 10-XXX codes when they ran out. All the three-digit codes became 101-0XXX after the switch, causing many people to think the ten-codes were now ten-ten codes. The ten-codes themselves came about due to the deregulation of long-distance telephone service which required local carriers to allow access to any long-distance carrier by dialing a special code. AT&T’s was 10-288 (ATT) for example. Then later cut-rate LD operations would spring up and get a 10-code and make amusing advertising jingles and then usually go bankrupt.)

Did they use the term Centrex, maybe?

If so, then the software (translations) for your phones lives in the provider’s switch. They have a “vanilla” plan that requires dialing 9 for “plain old telephone” (POTS) access. It could just as easily be 8 or 6 or 103, actually. It’s called an “Individual Dialing Plan”.

The dialing plans can get pretty complicated when customers have multiple locations and use dedicated private routes. Every phone has to have it’s own set of permissions to use different features, get access codes to use specific networks, etc.

To follow up on my first post, it’s business service. As far as I know, I must always dial 9. It’s not a situation where I can call the guy down the hall by dialing his extension without a 9.

I believe so, yes.

Ok, but why require anything at all? Why not just let the system dial 9 automatically for me?

One of the main centrex features is 3-or-4 digit dialing in between stations. The switch needs to be able to figure out if you’re dialing your boss’s extention or if you’re calling someone outside of your dialing plan. So, the translations say,

“When a user dials 9, give them back a second dial tone and expect 6 (or more) digits to complete a regular (POTS) call.”

“When a user dials [for example] 4, expect three more digits and complete the call via the translations in individualized dialing plan.” Which means…

…the IDP translations take the 4 digits of your boss’s extention, say “1234”, then add the appropriate prefix back on, say “555”. Voilà, you have 555-1234–the seven-digit number is reconstituted, and the switch completes via the “Intercom Use” feature embedded in the centrex.

Note: this explanation is based on the software found in a Lucent 5ESS switch.

If you have a business that does lots of overseas calling, you really don’t want a dial nine to get an outside line system.
Why you ask?
Your employee dials 9 to get outside, and then is supposed to dial 011 for international access.
Murphy being Murphy makes the employee miss or forget to dial the 0. Employee dials 911. System is set up that 911 goes outside right now in case of fire or whatever.
Nice police officer shows up. After a few dozen of these, company gets charged.
Ask me how I know this.

:smack: :smack: Crap, missed the typo. It should read 7 or more digits. (in the USA)


Depending on the centrex, 911 might have it’s own entry in the IDP.

Seems like a reasonable explanation, except that as far as I know, my plan has no 3 or 4 digit dialing. If I dial 3 or 4 digits without the “9,” I just get one of those “your call cannot be completed” messages.