5ESS Digital (ISDN) Telephone User Guide
Overview
This guide describes how to use the voice features of the Lucent/AT&T
ISDN (Integrated Services Digital Network) digital telephone with
MIT's 5ESS telephone system. These features will work only when
your Lucent/AT&T telephone is correctly connected to the 5ESS.
In addition to standard voice communications, digital telephones
can carry data communications between a microcomputer or workstation
that is connected to the telephone and a remote computer.
Telephone Customer Service
To provide fast and efficient service each MIT department is assigned
a Customer Service Representative (CSR). Your CSR can be reached
at 617.253.3670.
Telephone HELP Line
If you have trouble with telephone or data communications service,
call the Telephone HELP desk at 617.253.4357 (x3-HELP).
Voice Mail
MIT's voice mail system works in conjunction with the 5ESS telephone
system. Voice mail is a computer-based message system that goes
beyond the functions of the usual answering machine. Voice mail
lets you send, forward, and reply to messages; send messages to
a distribution list; archive messages; and give special access to
a secretary. For details on voice mail services and how to order
them, please see the Voice
Mail User Guide. You can get assistance with your voice mail
from your CSR at 617.253.3670.
Your Digital Telephone
Desk Set
Desk Set Controls and Features
This section describes the digital phone's components. Terms that
are discussed in this and later sections are introduced in italics.
Also included are information and procedures for desk set controls
and features that apply to all types of calling.
Lucent/AT&T digital desk sets come in two models: the ISDN
7506 and the ISDN
7507. The 7507 model is larger than the 7506, with more buttons;
otherwise, their functions and use are identical.
Note: If your ISDN desk-set model is 8510, see the ISDN 8510T Voice Terminal
User's Manual for details on features
and components.
To avoid interruptions in phone service:
- Never unplug your desk set.
- Never plug another desk set into your phone jack.
- Never plug any accessory into your desk set.
- Never plug the receiver into any other jack.
Digital desk sets have two types of buttons: Call Appearance
and Feature. Press near the center of a button to activate
it. If you wish to change button labels, follow the instructions
on the bottom of the desk set.
Call Appearance (CA) Buttons
Call Appearance (CA) buttons are used to place and receive phone
calls, including intercom calls. Each CA button has two status
lights associated with it. The red light indicates the CA is
in use, or will be used when the receiver is lifted. The green light
indicates that a call is in progress or a feature has been activated.
CAs are labeled with a directory or an intercom number.
Directory Number (DN)
A directory number is a telephone number. Calls placed within
MIT from an MIT phone require only the five-digit MIT number (beginning
with the prefix 2-, 3-, 5-, 8-, or -7). Calls to MIT from off-campus
require the full ten-digit MIT phone number (beginning with the
prefix 225-, 252-, 253-, 258-, 324-, or 577-).
Primary Directory Number (PDN)
Each digital desk set is assigned a primary directory number (PDN).
The PDN is usually the MIT phone number for the person or office
"owning" the desk set.
Secondary Directory Number (SDN)
A secondary directory number (SDN) is any number other than the
primary directory number that appears on a telephone. SDNs may be
additional numbers assigned to a phone or numbers shared with other
phones. SDNs cannot have voice mail.
Call Appearance Assignments
Digital technology makes it possible to assign the same directory
number to more than one Call Appearance button. Your PDN is always
assigned to a minimum of two CAs on your desk set. This means that
you can have at least two calls going at once, even though your
telephone is set up for only one directory number.
The last CA of a number is reserved for outgoing or intercom calls.
If your PDN has only two CAs, calls can usually come in only on
the first CA. If you have answered or placed a call on the first
CA, a second call can't come in. When placing calls you can leave
the first CA open for incoming calls by pressing the second CA of
your PDN before making the call.
If you receive many calls you may want to opt for one of two permanent
solutions. You can modify the second CA to receive incoming calls,
or you can add a third CA. Call your Customer Service Representative
for details and costs.
Feature Buttons
Feature buttons activate special functions of the digital telephone.
Features are either fixed or flexible.
Fixed Feature Buttons
Most Fixed Feature buttons control two functions: one for processing
calls and an alternate function for controlling the desk set. Fixed
Features for call processing work with any type of call, on PDNs
or SDNs. You select alternate functions by pressing Shift/Select
first. Refer to the appropriate section in this guide for details
on fixed features. Some Fixed Feature buttons have a green status
light associated with them.
Flexible Feature Buttons
Flexible Feature buttons activate functions other than fixed features;
for example, call pick-up and speed dialing. You request flexible
features when ordering new service or additions to existing service.
Flexible Feature buttons are installed only on those phones for
which they are ordered, and work only with a desk set's PDN.
Other Desk Set Features
In addition to Call Appearance and Feature buttons, the digital
desk set includes the following components.
Dialing Keypad
Use the alphanumeric keypad for entering telephone numbers and code
numbers. The keypad is also used with the voice mail system. Two
keys have special functions in both the 5ESS and voice mail systems:
"Star" or asterisk key |
|
"Pound" or number key |
|
Display Panel
The display panel is a small screen at the top of the desk set (with
a knob to adjust its contrast). It displays the date and time when
the phone is not in use, or displays information about calls when
in use. For details, see Section 9, "The
Display Panel."
Message Light
If you subscribe to voice mail, the Message light indicates that
new messages are in your voice mailbox.
Data/Send/Off Button
The Data/Send/Off button carries data communications between a microcomputer
or workstation connected to the digital set and a remote computer.
Data calls do not interfere with placing or receiving voice calls
-- they can occur simultaneously.
Speakerphone
The Speakerphone lets you place and answer calls without lifting
the receiver. The microphone and speaker are located in the desk
set, under the receiver. When using the Speakerphone, speak toward
the front of the desk set.
1. To activate the Speakerphone, press |
|
2. To disconnect, press |
|
then press |
|
Adjusting Volume of Ringer and Receiver
The Volume button controls the loudness of your phone's ring, and
the voice level of the receiver and Speakerphone. You can change
the loudness of the phone's ring whenever you are not on a call.
You can change the voice level of the receiver or speaker only when
you are on a call.
1. Press the |
|
arrows until you hear the desired volume. |
| Left arrow lowers the volume; right arrow
raises the volume.
Result: Each press adjusts the volume. |
Digital Phone Options
The 5ESS and the digital telephone provide optional features and
services that you can order as new service or changes to existing
service. Two call-handling options, ringing line preference
and reserved call appearances, are described below. Other
options -- intercom calling, call
pickup groups, and speed dialing
-- are explained in their own sections elsewhere in this guide.
For more information on these options, and other options not covered
in this guide, contact your Customer Service Representative.
Ringing Line Preference
With ringing line preference you
do not have to press a CA to answer or place a call -- the appropriate
CA will be selected automatically when you lift the receiver or
press Speaker. If you are on a call and another comes in, put the
first call on hold and press Drop to connect to the second call.
Ringing line preference is not recommended for digital desk sets
carrying more than one phone number.
Reserved Call Appearance
All CAs for directory numbers let you place and receive calls (two-way
calling). With reserved Call Appearance, you can, however, order
one CA reserved for one-way calling. Choose from the following types
of reserved CAs.
• Originate: You can use the CA to place outgoing calls
only; calls cannot be received on it.
• Terminate: You can use the CA to receive incoming calls
only; calls cannot originate from it.
• Originate/Priority Terminate: You can use the CA to place
outgoing calls, or to receive intercom (priority) calls.
For example, your PDN is assigned three CAs on your desk set and
you have reserved one of those as Originate/Priority Terminate.
If two CAs are active with calls, the third CA can be used only
to place a call or receive an intercom call. In such circumstances,
a regular incoming call will get a busy signal.
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Telephone Calls
Placing a Call
You place outgoing calls from your primary directory number (PDN)
or a secondary directory number (SDN). If you are not on a call,
the red light of the call appearance (CA) you will be using is on.
If you wish to use a different CA, press another CA button.
1. Lift the receiver or press |
|
Result: The green light of the CA you
selected comes on and you hear the dial tone. |
| 2. Dial the telephone number. |
Answering a Call
The phone rings and the green light flashes on the CA carrying
the call.
1. Lift the receiver or press |
|
2. Press the CA button with the flashing
green light. |
Result: The red light comes on for that
CA and you are connected to the caller. |
Note: If you are on a call when another
comes in, the phone rings only once, but the green light for
the CA carrying the call flashes. To answer the second call,
put the first call on Hold, then press the second call's CA. |
Putting a Call on Hold
Both status lights of the CA you are using are on.
1. Press |
|
Result: The red light of the CA goes
out and the green light blinks rapidly. The call is on hold.
Press another CA to place a call, or press the CA with the
green flashing light to answer a call. |
Return to a Held Call
The green light of the held call's CA blinks rapidly.
1. Press the CA button for the held call. |
| Result: The red light comes on and the green light
stops blinking. You are reconnected to the call.
Note: If the call was put on hold at a digital set,
you can reconnect on another digital set with the same DN
(PDN or SDN). If the call was put on hold at an analog set,
you can reconnect only on that phone. |
Transferring
a Call
You can transfer an active call (not on hold) to another phone
on campus.
1. While on the active call, press |
|
Result: You hear the dial tone. The
red light for that CA goes off, the green light blinks rapidly.
The call is held for transfer. You are given an available
CA. If the call is on a DN with no other CAs available, select
an available CA of another number. |
2. Dial the MIT telephone number to which
you want to transfer the call. |
3. When the call is answered, announce that you are
transferring a call and press |
again. |
Result: The call is transferred. |
Placing a Conference
Call
You can set up a three-way conference call from your digital phone
with two other parties on or off campus.
1. While on the active call, press |
|
Result: The call is held for conference.
The red light for that CA goes off, the green light flutters.
The next available CA for that DN is selected and its red
and green lights come on; you hear the dial tone. If the call
is on a DN with no other CAs available, select an available
CA of another DN. |
2. Dial the number of the third party to
add to the call. |
3. When the third party answers, announce the conference
call and press |
again. |
Result: You are connected to the other
two parties. |
Activate Muting
Muting prevents the party on the other end of a call from hearing
a conversation at your end. Muting works with both the Speakerphone
and the handset, and is more effective than putting your hand over
the mouthpiece.
1. While on a call, press |
|
Result: The Mute green light comes on
and the person on the other end of the call cannot hear you,
although you can still hear them. |
2. To cancel muting, press |
again. |
Result: The Mute green light goes off
and the person on the other end of the call hears you. |
Number Privacy
See Telephone
Features
Redial the Last Number Entered
This feature redials the last phone number entered.
1. Lift the receiver or press |
|
Result: You hear the dial tone. |
2. Press |
|
Result: The last number you entered
is redialed. |
[Back to top]
Intercom Calls
Intercom Service
The 5ESS provides for three types of intercom calls:
• Automatic -- intercom between two pre-determined parties.
• One-digit Dial -- intercom group of up to ten parties.
• Two-digit Dial -- intercom group of up to twenty parties.
If your desk set is equipped for intercom calling, one of its CAs
is labeled as an intercom button. Intercom calling is an option
that you request when ordering new service or changing existing
service. Destinations and calling codes are set when intercom service
is installed or changed. Call your Customer Service Representative
for details.
Placing Intercom Calls
Follow the procedures below for the type of intercom installed
on your phone.
Automatic Intercom
Automatic Intercom service connects you to a predetermined party.
1. Lift the receiver or press |
|
2. Press |
|
Result: The Intercom green light comes
on and the 5ESS dials the intercom call. |
One-digit Dial Intercom
One-digit Dial Intercom service includes up to ten parties. The
intercom destinations are assigned code numbers 0 (zero) through
9.
1. Lift the receiver or press |
|
2. Press |
|
Result: The Intercom green light comes
on. |
3. Enter the one-digit code of the desired
party. |
Result: Your intercom call is placed. |
Two-digit Intercom
Two-digit Dial Intercom service includes up to ninety-nine parties.
The intercom destinations are assigned code numbers 01 through 99.
1. Lift the receiver or press |
|
2. Press |
|
Result: The Intercom green light comes
on and you hear a stutter dial tone. |
3. Press
|
and enter the two-digit intercom code of the desired party. |
Result: Your intercom call is placed. |
Receiving Intercom Calls
A single, steady beep is the signal for an incoming intercom call.
For Automatic and One-digit Dial Intercoms, the green light flashes
on both the PDN CA and the intercom button; for Two-digit Dial Intercoms,
the green light flashes on the Intercom-In button.
1. Lift the receiver or press |
|
2. For Automatic and One-digit Dial Intercoms,
press the CA button with the flashing green light. |
For Two-digit Dial Intercoms press |
|
Result: The respective red light comes
on and you are connected to the intercom call. |
[Back to top]
Call Forwarding
Forwarding to an On-campus Phone
This section describes call forwarding and explains how to activate
and cancel it. You can change call forwarding as your call coverage
needs dictate. You can forward incoming calls to another MIT phone
number, including the voice mail system if you are a subscriber.
For details on call forwarding for voice mail, see the User's
Guide to the MIT Voice Mail System (TC-1).
Call Forwarding Conditions (On Campus)
The following table described the call forwarding conditions and
gives the codes to activate and cancel each one. You can have
any combination of call forwarding conditions active at one time;
however, forwarding of all calls supersedes any other active
forwarding.
| Forwarding Condition |
Activate |
Cancel |
Unanswered calls
(your phone rings before it is forwarded) |
 |
 |
| Incoming calls encountering a busy signal |
 |
 |
| All calls (your phone doesn't ring) |
 |
 |
If you forward unanswered calls, you can change the number of
times the phone rings before forwarding takes place; see instructions below.
Activating Call Forwarding
To activate one call forwarding condition, follow this procedure.
Repeat the procedure to activate additional conditions. Call forwarding
remains in effect until you cancel it.
1. Lift the receiver and listen for the dial tone. |
2. Enter the appropriate two-digit activation code
(see call forwarding table above). |
3. Enter the five-digit MIT phone number to which
calls will be forwarded. If forwarding to voice mail, enter
8-6245.) |
Result: You hear a confirmation tone of two quick
beeps, followed by the dial tone. If you are forwarding
to another phone, the 5ESS places a confirmation call to
that number; the call does not have to be answered. If you
are forwarding to voice mail, no confirmation call is placed. |
Note: If you get a busy signal after entering
the activation code, call forwarding for that condition
is already in effect. Enter the cancellation code for that
condition and start over. |
Canceling Call Forwarding
To cancel call forwarding for one condition, follow this procedure.
Repeat the procedure to cancel additional conditions.
1. Lift the receiver and listen for the dial tone. |
2. Enter the appropriate two-digit cancellation code
(see call forwarding table above). |
Result: You hear a confirmation tone of two quick
beeps, followed by the dial tone. |
Changing Number of Rings Before Forwarding
Once you activate the forwarding of unanswered calls (code 78),
the system forwards a call after five rings of your telephone,
or twenty seconds. You can change the number of times your phone
rings (actually, the elapsed number of seconds) before a call
is forwarded.
In the procedure below, enter the number
of seconds, from the following table, to get the desired number
of rings before forwarding (1 ring = 4 seconds):
| Seconds |
Rings |
08 |
2 |
12 |
3 |
16 |
4 |
20 |
5 |
1. Lift the receiver and listen for the dial
tone. |
2. Press 
|
plus the desired number of seconds from the
table above. |
Result: You hear a short confirmation
tone of two quick beeps, followed by the dial tone |
Example: To have unanswered calls forwarded after
four rings, press |
|
Forwarding to an Off-campus Phone
If your PDN has off-campus calling privileges (Classes A or B),
you can forward calls to an off-campus telephone. If you are unsure
of your class of service, check with your Administrative Officer.
Call Forwarding Conditions
(Off Campus)
The following table described the call forwarding conditions and
gives the codes to activate and cancel each one. You can have
any combination of call forwarding conditions active at one time;
however, forwarding of all calls supersedes any other active forwarding.
| Forwarding Condition |
Activate |
Cancel |
Unanswered calls
(your phone rings before it is forwarded) |
|
|
| Incoming calls encountering a busy signal |
|
|
| All calls (your phone doesn't ring) |
|
|
Activating Off-campus Call Forwarding
To activate one call forwarding condition, follow this procedure.
Repeat the procedure to activate additional conditions. Call
forwarding remains in effect until you cancel it. Note: The
code in step 3 is required before entering the off-campus number.
1. Lift the receiver and listen for the dial
tone. |
2. Enter the appropriate two-digit activation
code (see call forwarding table above)
|
Result: You hear the dial tone again |
3. Press  |
plus the off-campus phone number to which calls will
be forwarded, including area code.
|
Note: You do not press 9, as you would
for normal off-campus calls. |
Result: You hear a confirmation tone
of two quick beeps, followed by the dial tone. The 5ESS
places a confirmation call to the forward-to number; this
call does not have to be answered. (If you don't have off-campus
calling privileges, you hear a fast busy signal.) |
Note: If you get a busy signal after
entering the activation code, call forwarding for that condition
is already in effect. Enter the cancellation code for that
condition and start over. |
Canceling Off-campus Call Forwarding
To cancel call forwarding for one condition, follow this procedure.
Repeat the procedure to cancel additional conditions.
1. Lift the receiver and listen for the dial tone. |
2. Enter the appropriate two-digit cancellation code
(see call forwarding table above). |
Result: You hear a confirmation tone of two quick
beeps, followed by the dial tone. |
[Back to top]
Call Pickup Group
Call Pickup
Call Pickup lets you can answer calls to other phones in a group
from your phone. It is intended for areas where people are close
enough to hear each other's phones ring, and where they can provide
occasional call coverage for each other. For details on setting
up a call pickup group, contact your Telephone Support Services
Customer Service Representative.
Answering a Pickup Group Call
Call Pickup is activated on a per call basis, and is canceled when
you hang up.
1. When you hear a group member's phone ring, lift the
receiver or press |
|
2. Press |
|
Result: You are connected to the call. |
[Back to top]
Speed Dialing
Creating a Speed Dialing List
Speed Dialing is a shortcut way to dial frequently-called telephone numbers by assigning Speed Call codes to your
frequently dialed telephone numbers. Two digit speed dial allows creating list of up to 100 numbers. If you already
have a two-digit intercom and want to use two-digit speed dialing, send email to telecom-csr@mit.edu or
call 3-3670.
1. Lift the receiver. |
2. Enter the Speed Dial Program code:  |
| 3.
Listen for dial tone again. (If you do not get a dial tone, then send e-mail to telecom-csr@mit.edu or
call 3-6370, requesting no charge activation of speed dialing.) |
4. Assign a two-digit code from 00 (zero-zero) to 19. (If the 2-digit code is already in use, you will
not get a message; the new phone number will overwrite the existing information.)
|
| 5. Enter the telephone number you are programming:
--For an on-campus number, enter the five-digit extension,
beginning with 2-, 3-, 5-, 8-, or 7-.
--For an off-campus number, enter 9 and the complete number
as you would normally, including the area code. |
Result: You hear a confirmation tone
of short beeps, followed by the dial tone. The number is saved
for Speed Dialing with the 2-digit code you entered. |
Placing a Call with Speed Call Codes
To place a call with Speed Dialing, follow this procedure.
1. Lift the receiver. |
2. Press |
2. Enter the appropriate Speed Call code for
the desired telephone number. |
Result: The full telephone
number associated with the Speed Call code is dialed; the number you are calling will show on phone display.
|
[Back to top]
Ring, Clock, and Test Buttons
Selecting a Ring Pattern
Your digital phone has eight different ring patterns. This helps
avoid confusion over incoming calls if several phones are near each
other.
1. Press |
|
2. Press |
|
Result: You hear the current ring pattern. |
3. Press |
|
| Result: You hear the next ring pattern.
Repeat step 3 to hear each successive ring pattern. |
4. When you hear the ring pattern you want, press |
|
Result: The desk set beeps twice. Your
phone will now ring with the selected pattern. |
Setting the Clock
The date and time are shown on the phone's display panel when you
are not on a call. You can change any part or all of this display.
1. Press |
|
2. Press |
|
Result: The month is shown on the display. |
3. Press |
until the correct month is shown. |
4. Press |
to save the month. |
| Result: The date is shown on the display.
Repeat steps 3 and 4 to change and save the date, hour, and
minutes, respectively. (Do not change the year unless
it needs to be increased to the current year!) |
4. Press |
to start the clock. |
Result: The desk set beeps twice and
the clock starts running. |
Activating the Phone Test
The test checks the Message and other lights, and the various tones
on your desk set. If any steps in the test fail or your service
is affected, call the Telephone Support Services HELP line at x3-4357
(x3-HELP).
1. Press |
|
2. Press |
|
Result: The green Message light comes
on and a tone begins repeating. |
3. Lift the receiver and press each button
on the telephone. |
| Result: Each light next to a button
should come on. You should hear a tone when you press buttons
without lights. If these signals do not work, your phone has
failed the test. |
Canceling the Phone Test
You can cancel the phone test at any time during its execution.
1. Press |
|
2. Press |
|
Result: The test is canceled. |
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The Display Panel
Display Information
A display panel is at the top of the digital desk set. When a call
is not in progress, the panel shows the date and time of day. When
a call is being placed or received, information about the call is
displayed, as shown on the diagram below (details on each part of
the display follow):
- Letter designating which CA is carrying the call.
- On outgoing calls, the number you enter; on incoming calls,
information on the origin of the call.
- A Call Identifier that defines the type of call.
- Elapsed time of the call.
Display Panel Contrast Adjustment
To the right of the display panel is a wheel for adjusting the contrast
of the display. Turn the wheel upward to darken the contrast; turn
the wheel downward to lighten it. Experiment with the contrast adjustment
to get the best display for your lighting conditions.
Call Appearance Designations
For all calls, a green light indicates which Call Appearance (CA)
button carries the call. On the display panel, the CA carrying a
call is also identified by a letter:
- On the Model 7506 desk set, the nine CAs are designated by the
letters a through j.
- On the Model 7507 desk set, the thirty CAs are designated by
the lowercase letters a through z and the uppercase
letters A through D.
Directory Number
When you place a call, the display shows the digits as you enter
them. When you receive a call, information on the origin of the
call is displayed. For calls received from an on-campus phone, that
phone's number is shown unless the caller has disabled such identification,
in which case PRIVATE NUMBER is displayed (see "Number
privacy"). Calls received from off-campus phones are shown
as INCOMING CALLS. Additionally, number privacy works when calling
off-campus numbers on phones that have caller ID.
Call Timing
Once an incoming or outgoing call is answered, the elapsed time
of the call in hours, minutes, and seconds is shown in the lower-right
portion of the panel.
Call Identifier
Codes
When you place or receive a call, Call Identifier codes are shown
in the upper-right portion of the display panel. The table below
lists, alphabetically, the most frequently encountered codes and
their meanings.
| Code |
Meaning |
| CFA |
Call Forwarding - All Calls |
| CFB |
Call Forwarding - Busy |
| CFN |
Call Forwarding - No Answer |
| HLD |
Call on Hold |
| ICM |
Intercom Call |
| InI |
Incoming Call - Internal (within MIT) |
| InX |
Incoming Call - External (outside MIT) |
| OnL |
On Another Line (a call forwarded to your
phone because of a No-Answer on the number being called)
|
| OuI |
Outgoing Call - Internal (within MIT) |
| OuX |
Outgoing Call - External (outside MIT) |
| Pck |
Call Picked Up |
| Pri |
Priority Call |
| TiL |
Tie-Line Call |
Call Forwarding Identification
When you place a call that gets forwarded, a Call Forwarding identifier
is displayed (see above).
When you receive a call that is being forwarded to you, the display
includes the origin of the call, the number of the phone from which
the call is forwarded, and a Call Forwarding identifier.
When you answer a call to an SDN on your desk set, an asterisk
(*) after the Call Identifier code means that the PDN phone for
that number is busy.
[Back to top]
Appendix A: Classes of Telephone Service
Below are descriptions of MIT's classes of phone service, including
restrictions on calling. If you are unsure which class of service
is on your phone, check with your department's Administrative Officer,
or call your Telephone Support Services Customer Representative.
If you try to place a call outside the restrictions of your service
class, you will hear a recording or a fast busy signal.
|
Class of Service |
Description |
| A |
Completely unrestricted. Can call world-wide
without using account numbers. Account numbers can be used
to bill a toll call to a particular MIT account. To call off-campus,
press 9 + complete phone number, including area or country
codes. |
| B1 |
Can call worldwide with an MIT account
number. For domestic toll calls, including all Massachusetts
area codes, press 191 + MIT account + 1 + area code and phone
number. For international calls, press 192 + MIT account +
011 + country code + city code + phone number. |
| B2 |
Can call only within the 617/857 and 781/339
area codes. To call within these area codes, press 9 + phone
number. (Class A or B1 are needed to call the 508/774, 978/351,
and 413 area codes.) |
| C |
Restricted to calling only within MIT.
Calls outside of MIT require the use of a telephone credit
or calling card. |
| D |
Reserved for selected applications, such
as emergency and elevator telephones. When the receiver is
lifted, the call is automatically placed to a predetermined
destination. Class D phones can receive calls only within
MIT. Not available for digital phones. |
| E |
Generally reserved for computer dial-up
applications. Restricted to placing and receiving calls only
within MIT. No access to toll operators or tie lines. |
| F |
Generally reserved for lobby phones. Restricted
to placing and receiving calls only within MIT. Access to
toll operators and tie lines is allowed |
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|
