few seconds. This condition is not abnormal during
periods of heavy traffic.
Any standard 600-ohm telephone can be used in
Within the ship, disconnect can only occur when
the system. The type G telephone is normally used, but
both the calling and the called parties hang up.
the other types are suitable.
Ship-to-shore disconnect occurs when the ship's
All telephone numbers used in the system have
station hangs up, regardless of what the shore station
three digits. They consist of a hundreds, a tens, and a
units digit. They are preassigned during installation,
EMERGENCY.-- Any telephone dialing 211
but may be changed by a wiring change. Each station
will automatically be connected to the predetermined
should be supplied with a copy of the ship's telephone
emergency station for that time period. This cut-in
directory. The directory is unique to a particular ship.
happens even if the emergency station is busy. The
A person using the telephone system will hear four
emergency stations are 201 quarterdeck, 203 alternate
distinct tones from the receiver during normal
quarterdeck, or 222 pilothouse. The station to receive
operation. These tones give information to the status
emergency calls is determined by a three-position
of a call. These tones are as follows:
switch at the central office switchboard.
Dial Tone. 600 Hz interrupted 120 ips. The
RESTRICTED LINE.-- Telephone stations
telephone is off-hook and the central office
connected as restricted are prevented from accessing
switchboard is ready to receive dial pulses.
the manual switchboard; therefore, they are unable to
connect to shore lines. This feature is established for
Busy Tone. 600 Hz interrupted 60 ips. The
a station at the central office switchboard. If a
called station is off-hook or all trunks/links are
restricted station tries to call the manual switchboard,
a busy tone will be returned. Additionally, if the
Ring-back Tone. 333 Hz modulated with 20 Hz
manual switchboard attendant calls a restricted line, a
interrupted at the same rate as the ringing
busy tone will be returned.
period (1 1/4 seconds on, 2 3/4 seconds off).
EXECUTIVE CUT-IN.-- Executive cut-in
The ringing voltage is being sent to the called
allows a station to complete a call even if the called
station is busy. This feature is also known as executive
right-of-way. The cut-in connection does not
Howler Tone. 600 Hz interrupted at 8 ips. The
disconnect the original call, just joins it. To obtain
howler tone is a loud, raucous sound intended
cut-in, the user dials the digit 1 after getting a busy
to alert personnel across the compartment or in
tone. This feature is established for a station at the
the next compartment of the situation. There-
central office switchboard.
fore, it is uncomfortable if the receiver is held
close to the ear. You should avoid the condi-
HUNT-THE-NOT-BUSY.-- A telephone dialing
tions that make the howler sound. These condi-
a number in a hunt-the-not-busy group will be
tions are as follows:
connected to the next higher idle number in the group
if the called number is busy. The numbers in the group
-- Telephone receiving dial tone and dialing is
must have consecutive units digits with common
not started in 30 seconds.
hundreds and tens digits. For purposes of this feature,
-- More than 30 seconds elapses between dialed
the O is the highest number in the units digit group. If
the search reaches the O, and it is busy, a busy tone is
returned to the caller. This feature is established for a
-- Busy tone is received for more than 30
chosen group of numbers at the central office
Hanging up the offending telephone will silence
the howler and return the telephone to normal status.
If the telephone is not hung up within 2 minutes, an
alarm sounds in the central office switchboard.
The tools and test equipment required to trouble
shoot and repair the central office telephone system
Sometimes due to the number of calls in process
are listed in table 6-14.
at the same time, the dial tone may be delayed for a