The Telephone Network


Sam Carpenter, September 8, 2016

Our telephone answering service client base of over 1,300 accounts is spread across the United States.  Clients, no matter where they are located, are served by the local phone company in their region: either a Local Exchange Company (LEC) or a Competitive Local Exchange Company (CLEC).

The key facility for any telephone company is the central office (CO). Each Central Oregon community for example, including Bend, has a single CO. Bend’s CO is located one block north of our Greenwood office on NW Kearney Ave. It is maintained by the local exchange carrier, Century Link. In contrast to the relatively small communities of Central Oregon, there are dozens of CO’s in large metropolitan regions such as Portland or Boston. The larger the population in a given area, the more CO’s will be found. Each CO serves the geographical region immediately surrounding it. The Verizon CO that services our customers in Portland has an AT&T-5AESS switch, which is considered a very up-to-date and efficient switch. The Bend Century Link CO has a Northern Telecom DMS-100 switch. It’s a good switch not so up-to-date…There are numerous types of CO switches but the two mentioned here comprise most of the CO switches in the Northwest.

Every phone line in a given area is connected to its local CO. When making a call, the caller picks up a phone which connects that caller via “dial-tone” to the CO. The CO is essentially a large computer connected to a “switch.” The switch can transfer calls according to the computer’s instructions. The caller hears dial-tone, which is the CO’s way of saying, “you can program me now.” The caller programs the CO switch by pressing keypad digits. The CO translates the keypad tones to numbers and then transfers the call to the desired destination. If the caller dials an area code as part of the number, the CO upon gathering the area code, immediately transfers the call to the CO within that area code; the local CO continues to process the call to its destination. A long distance call routes through numerous CO’s before it arrives at its final destination.

Centratel’s phone lines are connected to the Bend CO switch via three PRI (“One Number”)/DID circuits. Each circuit has 23 “talk paths” that enable us to process a total of 69 simultaneous calls through our telephone answering service and/or one of our two voice mail systems. Most remote location telephone answering service calls come to our office via PRI (“One Number”) format. Most Central Oregon telephone answering service and all Central Oregon voice mail traffic is transmitted to our office via DID trunk protocol.

Centratel Equipment and Call Processing

At Centratel, we have an “internal” switch.  Our switch is manufactured by Startel. Like the CO, the Startel system consists of a computer interfaced with a switch mechanism which routes calls according to the computer’s instructions. Although much smaller than a CO switch, our Startel does essentially the same thing: it routes calls to various destinations.

Here is a summary of how a typical call is routed to one of our answering service Telephone Service Representatives (TSR’s): Customers are either assigned a Telco 10 digit DID number to which their main business line is forwarded, or they use PRI (“One Number”) technology and forward to our national toll-free PRI (“One Number”) number. The caller calls the client’s main office number and the CO for that area diverts the call, via call forwarding, to our Bend CO and then down the Centratel trunk group to the Startel switch in our equipment room. The Startel equipment “identifies” the call and then switches it to either a TSR workstation for immediate processing, or to our voice mail system for preliminary screening. Voice mail assisted accounts comprise approximately 5% of all telephone answering service accounts.

Voice Mail and the Telephone Answering Service

Our Startel switch is connected to two voice mail systems which serve hundreds of individual voice mail users. The voice mail system is connected to the Startel switch via “internal trunks.” There are three primary reasons for the voice mail component:

1. To allow our TSR’s to easily record a message for clients. The customer calls the mailbox directly to pick up the message.
2. To provide “Gold Service,” our term for a special option that routes a caller into the voice mail system for screening. Most of our medical, veterinary, and property management accounts use Gold Service. For these accounts, approximately 35% of all calls are processed in the voice mail and never reach a TSR. It’s a cost savings for the client and offers faster, better service for those callers who just want to find out when an office is open or simply wish to leave a message.
3. To take advantage of what we call “diversity.” Note that our regular “straight” voice mail accounts  have no direct need for the Startel switch: calls could be routed down a separate trunk group directly to the voice mail system. However, by using the same trunk group for voice mail accounts as we use for telephone answering service accounts, fewer total trunks are required. Two smaller trunk groups, with more total trunks, would not only be more expensive but in peak traffic periods would more often be at full capacity thus giving busy signals to callers.

Any voice mail message can be converted into a WAV file and delivered to the client via email.

Gold Service

Used by approximately 5% of our telephone answering service accounts, Gold Service works as follows: An incoming call travels to the Centratel switch, is identified, and then is forwarded intov voice mail system where a greeting is played for the caller. The greeting is specific to that particular account. The caller is given choices. If he or she chooses to speak to our TSR by pressing the zero key on their dial pad or by staying on the line, the call is routed from the voice mail system back to the switch. The switch then routes the call to the Startel call processing system. The Startel switch passes it, along with the account’s specific information, to a TSR for processing. Approximately 35% of incoming Gold Service calls do not require human interaction and are processed entirely within the voice mail system, never reaching a TSR.

For the Gold Service caller reaching voice mail first, there are usually three options:

  1. The caller can listen to information such as office hours and/or directions to the customer’s office.
  2. The caller is given the opportunity to leave a message in their own voice.
  3. The caller can choose to be transferred to a TSR for urgent call processing.

As mentioned above, with Gold Service accounts, approximately thirty percent of all incoming calls are processed in voice mail and never reach a TSR. The vast majority of calls that finally reach our TSR’s are calls that must be handled by a human being. Conversely, the calls handled by voice mail, are better processed in an automated system and do not require the relatively expensive intervention of a human. Compared to regular “straight live” telephone answering service, Gold Service is less expensive for the client and provides more options for their callers. For Centratel, it insures that TSR’s are only handling calls that require human intervention. Gold Service is used mostly by medical accounts, veterinary and property management companies.

“Modified Gold Service”: Note that, to screen calls, some answering service accounts use the voice mail system that is integral to their own office telephone system. Then, if the caller requires a TSR’s assistance, the caller is routed by the client’s phone system to our switch. In other cases, the client simply gives out our DID or 800 number for the caller to manually redial our service.

Message Alert

For either telephone answering service or straight voice mail accounts, we can set up a voice mailbox to page the user when a message is deposited in their mailbox. We can program the mailbox to repeatedly send out pages, at pre-determined intervals. Also, the mailbox can call the customer at home or on a cellular phone to deliver the message directly. The system can also be set up so that the caller can choose to have the pager activated for urgent messages only. Also, the voice mailbox can forward the message via WAV file to the user’s computer so the client does not have to call the mailbox to pick up the message. Another option is to have the mailbox simply notify the user via Email that a message is waiting (this feature is used extensively in our own internal Centratel communications).

Message Delivery Via Alpha Paging and Fax

If the Telephone Service Representative sends an “alpha” message, the Startel switch selects an outgoing trunk, dials out through a modem to the alpha pager “terminal” which is located at the client’s paging company. The paging terminal sends the alpha message to the customer’s pager via a network of antenna-equipped towers. If a message is faxed to a customer, it goes first through a special fax modem in our Startel switch and then to the customer’s fax machine. Faxes can be sent one at a time as the messages are processed by TSR’s or, with “batch” fax message delivery, the switch uses a pre-programmed schedule to send the faxes to the customer at designated times. Both batch fax and single message fax delivery can be used simultaneously by the same account. However, an account cannot use both fax and Email (see below) on the same account:: it has to be one or the other.

Message Delivery Via Email

Although the format is Email, the process is similar to fax message delivery (see above). Email is our favorite mode of message delivery as it is accomplished without using any telephone trunks to deliver the call, and it’s fast.