Telephone Line Emulator User’s Manual
40-400-00020, Rev. M 126
Off-hook
The telephone is in an off-hook state when the handset is removed from the cradle. A
modem or other device is off-hook when it answers a call or when it seizes a line to initiate
a call.
On-hook
a condition when the CPE is connected to a line and is not drawing loop current
Mark
Logical 1 or Symbol 1, equivalent to the lower of the two frequencies used in FSK
signaling
MDMF
Multiple Data Message Format. A Caller ID transmission scheme that consists of a
Message Header and a Message Body containing parameter messages. Generic
description is Name + Number Transmission.
OSI
Open Switch Interval, a time when the DC battery is removed from Tip and Ring
Polarity Reversal
A line condition where the battery polarity is reversed from its current state
Public Switched Telephone Network (PSTN)
Refers to the worldwide voice telephone network accessible to those with telephones and
access privileges. Also known as PTN, Public Telecommunications Network.
Reorder Tone
In North America the reorder tone that sounds like the busy signal, but is twice as fast. It
indicates that all switching paths are busy.
Ringback
The sound you hear when you are calling someone else’s phone. The tone you hear is
generated by a device at the central office and may not be synchronized to the sound the
phone at the other end is emitting - or not emitting.
RP-AS
Ringing Pulse Alerting Sequence. A short ring burst.
SAS
Subscriber Alerting Sequence, also known as Call Waiting Tone, this is an audible tone
issued to a Called Party indicating a Waiting Call.
SDMF
Single Data Message Format. A Caller ID transmission that consists of a Message Header
and a Message Body. Generic description is Number only Transmission.
Space
Logical 0 or Symbol 0, equivalent to the higher of the two frequencies used in FSK
signaling
TAS
TE Alerting Signal, consists of either DT-AS, RP-AS, or a line reversal followed by a DT-
AS
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