The Devices File

The Devices File

The Devices file (/etc/uucp/Devices) contains information for all the devices that can be used to establish a link to a remote computer, such as automatic call units, direct links, and network connections.

Note: This file works interdependently with the Dialers, Systems, and Dialcodes files. Before you make changes in any of these files, you should be familiar with them all. A change to an entry in one file may require a change to a related entry in another file. Each entry in the Devices file has the following format:

Type Line Line2 Class Dialer-Token-Pairs

Entries for use with modems should always have the form

Name device null speed 212 x dialer

Entries for use over TCP/IP network connections have the form

TCP - - Any TCP uucp

Devices file fields are defined in the following sections.

The Type Field

The keyword used in the Type field is matched against the third field of Systems file entries. The Type field can contain one of these keywords: Direct, ACU, or a station name.

Direct: This keyword indicates a direct link to another computer or a switch (for cu connections only).
ACU: This keyword indicates that the link to a remote computer is made through an automatic call unit (automatic-dial modem).
Sys-Name: This value indicates a direct link to a particular computer. (Sys-Name is replaced by the name of the computer.) This naming scheme is used to convey the fact that the line associated with this Devices entry is for a particular computer in the Systems file.

You can designate a protocol to use for a device within this field. See the "Protocols" section at the end of the description of this file.

The Line Field

This field contains the device name of the line (port) associated with the Devices entry. For instance, if the automatic dial modem for a particular entry is attached to the /dev/ttyf5 line, the name entered in this field is ttyf5.

You should always use the ttyf devices when working with modems. These devices support hardware flow control, which is used by all modems that support V.32 or V.32bis.

The Line2 Field

If the keyword ACU is used in the Type field and the ACU is an 801-type dialer, the Line2 field contains the device name of the 801 dialer. (801-type ACUs do not contain a modem. Therefore, a separate modem is required and must be connected to a different line, defined in the Line field.) The need for a separate modem line means that one line would be allocated to the modem and another to the dialer. Since non-801 dialers do not normally use this configuration, they ignore the Line2 field, but it must still contain a hyphen (-) or the word null as a place holder. A place holder is necessary for most modems.

The Class Field

The keyword used in the Class field of the Devices file is matched against the fourth field of Systems file entries:

Devices: ACU ttyf5 null D9600 212 x telebit

Systems: eagle Any ACU D9600 14155551212 login:nuucp password:Oakgrass

Some devices can be used at any speed, so the keyword ''Any'' can be used in the Class field. If Any is used, the line will match any speed requested in a Systems file entry. If this field is Any and the Systems file Class field is Any, the speed defaults to 9600 bps. If the keyword ACU or Direct is used in the Type field, the Class field might contain only the speed of the device. However, the speed can also be preceded by a letter (for example, C9600, D9600) to differentiate between classes of dialers (Centrex or Dimension PBX). Including the dialer class is necessary in larger offices that have more than one type of telephone network: One network may be dedicated to serving only internal communications while another handles external. In such a case, it becomes necessary to distinguish which line(s) should be used for internal and which for external.

The Dialer-Token-Pairs Field

This field contains pairs of dialers and tokens. The Dialer portion may be the name of an automatic-dial modem, or ''Direct'' for a direct-link device. You can have any number of Dialer-Token-Pair (DTP) fields. The Token portion may be supplied immediately following the Dialer portion; if not present, the Token portion will be taken from a related entry in the Systems file.

This field has the format:

dialer token dialer token

The last pair may or may not be present, depending on the associated device (dialer). In most cases, the last pair contains only a Dialer portion and the Token portion is retrieved from the Phone field of the Systems file entry. A valid entry in the Dialer portion may be defined in the Dialers file.

The DTP field can be structured in different ways, depending on the device associated with the entry.

If an automatic-dial modem is connected directly to a port on your computer, the DTP field of the associated Devices file entry will have only one pair. This pair is normally the name of the modem. This name is used to match the particular Devices file entry with an entry in the Dialers file. Therefore, the Dialer field must match the first field of a Dialers file entry:

Devices: ACU ttyf2 null 9600 212 x telebit
Dialers: telebit =&-% "" \r\p\r\c $ <K\T%%\r>\c ONLINE!

Notice that only the Dialer portion (telebit) is present in the DTP field of the Devices file entry. This means that the token to be passed on to the dialer (in this case the phone number) is taken from the Phone field of a Systems file entry. (\T is implied)

If a direct link is established to a particular computer, the DTP field of the associated entry contains the keyword Direct. This is true for both types of direct-link entries, Direct and System-Name.

If an automatic-dial modem is connected to a switch, your computer must first access the switch; the switch then makes the connection to the modem. This type of entry requires two Dialer-Token-Pairs. The Dialer portion of each pair (fifth and seventh fields of entry) is used to match entries in the Dialers file:

Devices: ACU ttyf2 null 9600 212 x t2500 telebit T25

Dialers: telebit "" "" \pr\ps\c est:\007 \E\D\e \007

Dialers: T25 =&-% "" \r\p\r\c $ <K\T%%\r>\c ONLINE!

In the first pair, t2500 is the Dialer and telebit is the token that is passed to the Develcon switch to tell it which device (telebit modem) to connect to your computer. This token is unique for each modem switch since each switch may be set up differently. Once the telebit modem has been connected, the second pair is accessed, where T25 is the dialer and the token (the telephone number) is retrieved from the Systems file. (See the discussion of the Systems file's Phone field in "The Systems File".)

Two escape characters can appear in a DTP field:

\T: Indicates that the Phone (Token) field should be translated by means of the Dialcodes file.
\D: Indicates that the Phone (Token) field should not be translated by means of the Dialcodes file. If no escape character is specified at the end of a Devices entry, the \D is assumed (default).

Device Protocols

You can define the protocol to use with each device. In most cases it is not needed since you can use the default or define the protocol with the particular station you are calling. (See the discussion of the Systems file, specifically the Type field.) If you do specify the protocol, you must do it in the form Type, Protocol. Available protocols are

g: This protocol is slower and more reliable than e. It is good for transmission over noisy telephone lines. This is the default protocol.
e: This protocol is faster than g, but it assumes error-free transmission, such as over a TCP/IP network connection.
t: This protocol, like e, is for use in an error-free environment, such as a TCP/IP network connection. The t protocol is used by systems running BSD UNIX operating systems.