Use of reference table ('look-up-table') and FK constraint

Hi,

In fits and starts I am working through converting a sybase schema ->
postgres and am hoping to gain some insight on the use of reference
tables ('look-up-table') and FK constraints.

In the example below I believe the sybase RULE Phone_type_rule is used
to restrict input, so that the only values which can be inserted or
updated into Phone have to be one of ('work', 'home', 'fax', 'mobile',
'lab', 'unknown').

How would this be accomplished using a look-up or reference table::FK
constraint combination?

CREATE RULE Phone_type_rule
AS @col IN ('work', 'home', 'fax', 'mobile', 'lab', 'unknown')
go

CREATE TABLE Phone (
phone_id Identifier_type IDENTITY,
phone_number varchar(20) NOT NULL,
community_id numeric(12) NOT NULL,
type varchar(10) NULL
)
go

exec sp_bindrule Phone_type_rule, 'Phone.type'
go

regards,

Charles