Cisco – Signaling

>Cisco – Signaling: “Signaling

Signaling is defined by Consultative Committee for International Telegraph and Telephone (CCITT) Recommendation Q.9 as ‘the exchange of information (other than speech) specifically concerned with the establishment, release, and control of calls, and network management in automatic telecommunications operations.’

In the broadest sense, there are two signaling realms:

* Subscriber signaling

* Trunk signaling (interswitch and/or interoffice)

Signaling is also traditionally classified into four basic functions:

* Supervision

* Address

* Call progress

* Network management

Supervision signaling is used to:

* Initiate a call request on line or trunks (called line signaling on trunks).

* Hold or release an established connection.

* Initiate or terminate charging.

* Recall an operator on an established connection.

Address signaling conveys such information as the calling or called subscriber’s telephone number and an area code, an access code, or a Private Automatic Branch Exchange (PABX) tie trunk access code. An address signal contains information indicating the destination of a call initiated by a customer, network facility, and so forth.

Call progress signals are usually audible tones or recorded announcements that convey call-progress or call-failure information to subscribers or operators. These call-progress signals are fully described below.

Network management signals are used to control the bulk assignment of circuits or to modify the operating characteristics of switching systems in a network in response to overload conditions.

There are about 25 recognized interregister signaling systems worldwide, in addition to some subscriber signaling techniques. CCITT Signaling System Number 7 (SSN7) is fast becoming the international/national standard interregister signaling system.

Most installations will probably involve recEive and transMit (E&M) signaling; however, for reference, single frequency (SF) signaling on Tip and Ring loops, Tip and Ring reverse battery loops, loop start, and ground start are also included.

Types I and II are the most popular E&M signaling in the Americas. Type V is used in the United States, but is very popular in Europe. Similar to type V, SSDC5A differs in that on- and off-hook states are reversed to allow for fail-safe operation: if the line breaks, the interface defaults to off-hook (busy). Of all the types, only II and V are symmetrical (can be back-to-back using a cross-over cable). SSDC5 is most often found in England.

Other signaling techniques often used are delay, immediate, and wink start. Wink start is an in-band technique where the originating device waits for an indication from the called switch before sending the dialed digits. Wink start normally is not used on trunks that are controlled with message-oriented signaling schemes such as Integrated Services Digital Network (ISDN) or Signaling System 7 (SS7).

Summary of Signaling System Applications and Interfaces

Signaling System Application/Interface Characteristics
Station Loop

Loop signaling

Basic Station

DC signaling.
Origination at station.
Ringing from Central Office.

Coin Station

DC signaling.
Loop-start or ground-start origination at station.
Ground and simplex paths may be used in addition to the line for coin collection and return.
Interoffice Trunk

Loop Reverse Battery

One-way call origination.
Directly applicable to metallic facilities.
Both current and polarity are sensed.
Can be used on carrier facilities with appropriate facility signaling system.

E&M Lead

Two way call origination.
Requires facility signaling system for all applications.
Facility Signaling System
Metallic DX
Analog SF
Digital Bits in information
Special Service

Loop Type

Standard station loop and trunk arrangement as above.
Ground-start format similar to coin service for PBX-CO trunks.

E & M Lead

E&M for PBX dial tie trunks. E&M for carrier system channels in special service circuits.

North American Practices

The typical North American touchtone set provides a 12-tone set. Some custom sets provide 16-tone signals of which the extra digits are identified by the A-D pushbuttons.

Dual Tone Multifrequency (DTMF) Frequency Pairs

Low Frequency Group (Hz) High Frequency Group (Hz)
1209 1336 1477 1633
697 1 2 3 A
770 4 5 6 B
852 7 8 9 C
941 * 0 # D

Audible tones commonly used in North America

Tone Frequencies (Hz) Cadence
Dial 350 + 440 Continuous
Busy (station) 480 + 620 0.5 sec on, 0.5 sec off
Busy (network) 480 + 620 0.2 sec on, 0.3 sec off
Ring return 440 + 480 2 sec on, 4 sec off
Off-hook alert Multifreq howl 1 sec on, 1 sec off
Recording warning 1400 0.5 sec on, 15 sec off
Call waiting 440 0.3 sec on, 9.7 sec off

Call Progress Tones Used in North America

Name Frequencies (Hz) Pattern Levels
Low tone 480 + 620
600 x 120
600 x 133
600 x 140
600 x 160 Various -24 dBm0
61 to 71 dBmC
61 to 71 dBmC
61 to 71 dBmC
61 to 71 dBmC
High tone 480
400
500 Various -17 dBmC
61 to 71 dBmC
61 to 71 dBmC
Dial tone 350 + 440 Steady -13 dBm0
Audible ring tone 440 + 480
440 + 40
500 + 40 2 sec on, 4 sec off
2 sec on, 4 sec off
2 sec on, 4 sec off -19 dBmC
61 to 71 dBmC
61 to 71 dBmC
Line Busy Tone 480 + 620
600 x 120
600 x 133
600 x 140
600 x 160 0.5 sec on, 0.5 sec off
Reorder 480 + 620
600 x 120
600 x 133
600 x 140
600 x 160 0.3 sec on, 0.2 sec off
6A alerting tone 440 2 sec on, followed by 0.5 sec on, every 10 sec
Recorder warning tone 1400 0.5 sec burst every 15 sec
Reverting tone 480 + 620
600 x 120
600 x 133
600 x 140
600 x 160 0.5 sec on, 0.5 sec off -24 dBmC
Deposit coin tone 480 + 620
600 x 120
600 x 133
600 x 140
600 x 160 Steady
Receiver off-hook (analog) 1400 + 2060 + 2450 + 2600 0.1 sec on, 0.1 sec off +5 vu
Receiver off-hook 1400 + 2060 + 2450 + 2600 0.1 sec on, 0.1 sec off +3.9 to -6.0 dBm
Howler 480 Incremented in level
Every 1 sec for 10 sec Up to 40 vu
No such number (crybaby) 200 to 400 Freq. modulated at 1 Hz interrupted every 6 sec for 0.5 sec
Vacant code 480 + 620
600 x 120
600 x 133
600 x 140
600 x 160 0.5 sec on, 0.5 sec off, 0.5 sec on, 1.5 sec off?
Busy verification Tone (Centrex) 440 Initial 1.5 sec followed 0.3 sec every 7.5 to 10 sec -13 dBm0
Busy verification Tone (TSPS) 440 Initial 2 sec followed 0.5 sec every 10 sec -13 dBm0
Call waiting tone 440 Two bursts of 300 ms separated by 10 sec -13 dBm0
Confirmation tone 350 + 440 3 bursts of 300 ms separated by 10 sec -13 dBm0
Indication of camp-on 440 1 sec every attendant releases from loop -13 dBm0
Recall dial tone 350 + 440 3 bursts, 0.1 sec on, sec off then steady -13 dBm0
Data set answer back tone 2025 Steady -13 dBm
Calling card prompt tone 941 + 1477 followed by 440 + 350 60ms -10 dBm0
Class of service 480
400
500 0.5 to 1 sec once
Order tones

Single

480
400
500 0.5 sec

Double

480
400
500 2 short bursts

Triple

480
400
500 3 short bursts

Quad

480
400
500 4 short bursts
Number checking tone 135 Steady
Coin denomination

3 5 cents

1050-1100 (bell) One tap

slot 10 cents

1050-1100 (bell) Two taps

stations 25 cents

800 (gong) One tap
Coin collect tone 480 + 620
600 x 120
600 x 133
600 x 140
600 x 160 Steady
Coin return tone 480
400
500 0.5 to 1 sec once
Coin return test tone 480
400
500 0.5 to 1 sec once
Group busy tone 480 + 620
600 x 120
600 x 133
600 x 140
600 x 160 Steady
Vacant position 480 + 620
600 x 120
600 x 133
600 x 140
600 x 160 Steady
Dial off normal 480 + 620
600 x 120
600 x 133
600 x 140
600 x 160 Steady
Permanent signal 480
400
500 Steady
Warning tone 480
400
500 Steady
Service observing 135 Steady
Proceed to send Tone (IDDD) 480 Steady -22 dBm0
Centralized intercept 1850 500 ms -17 dBm0
ONI order tone 700 + 1100 95 to 250 ms -25 dBm0

Note: Three dots in the pattern mean that the pattern is repeated indefinitely.

Single Frequency In-Band Signaling

SF in-band signaling is widely used in North America. Its most common application is for supervision, such as idle-busy, also called line signaling. It also can be used for dial pulse signaling on trunks. The dynamics of SF signaling requires an understanding of the signal durations and configurations of the E&M circuits, as well as the lead interface arrangements. The following tables show the characteristics of SF signaling, E&M lead configurations, and interface arrangements.

Typical Single Frequency Signaling Characteristics

General

Signaling frequency (tone)

2600 Hz

Idle state transmission

Cut

Idle/break

Tone

Busy/make

No tone
Receiver

Detector bandwidth

+/- 50 Hz @ -7 dBm for E type
+/- 30 Hz @ -7 dBm

Pulsing rate

7.5 to 122 pps

E/M unit

Minimum time for on-hook

33 ms

Minimum no tone for off-hook

55 ms

Input percent break (tone)

38-85 (10 pps)

E lead – open

Idle

– ground

Busy

Originating (loop reverse battery) unit

Minimum tone for idle

40 ms

Minimum no tone for off-hook

43 ms

Minimum output for on-hook

69 ms

Voltage on R lead (-48 V on ring and ground on tip)

On-hook

Voltage on T lead (-48 V on tip and ground on ring)

Off-hook

Terminating (loop reverse battery) unit

Minimum tone for on-hook

90 ms

Minimum no tone for off-hook

60 ms

Minimum output (tone-on)

56 ms

Loop open

On-hook

Loop closed

Off-hook
Transmitter

Low level tone

-36 dBm

High level tone

-24 dBm

High level tone duration

400 ms

Precut

8 ms

Holdover cut

125 ms

Crosscut

625 ms

On hook cut

625 ms

E/M unit

Voltage on M lead

Off-hook (no tone)

Open/ground on M lead

On-hook (tone)

Minimum ground on M lead

21 ms

Minimum voltage on M lead

21 ms

Minimum output tone

21 ms

Minimum no tone

21 ms

Originating (loop reverse battery) unit

Loop current to no tone

19 ms

No loop current to tone

19 ms

Minimum input for tone out

20 ms

Minimum input for no tone out

14 ms

Minimum tone out

51 ms

Minimum no tone out

26 ms

Loop open

On-hook

Loop closed

Off-hook

Terminating (loop) unit

Reverse battery to no tone

19 ms

Normal battery to tone

19 ms

Minimum battery for tone out

25 ms

Minimum reverse battery for no tone

14 ms

Minimum tone out

51 ms

Minimum no tone out

26 ms

Battery on R lead (-48 v)

On-hook

Battery on TY lead (-48 on tip)

Off-hook

Single Frequency Signals Used in E&M Lead Signaling

Calling End Called End
Signal M-Lead E-Lead 2600 Hz 2600 Hz E-Lead M-Lead Signal
Idle Ground Open On On Open Ground Idle
Connect Battery Open Off On Ground Ground Connect
Stop dialing Battery Ground Off Off Ground Battery Stop dialing
Start dialing Battery Open Off On Ground Ground Start dialing
Dial pulsing Ground Open On On Open Ground Dial pulsing

Battery
Off
Ground

Off -hook Battery Ground Off Off Ground Battery Off-hook (answer)
Ring forward Ground Ground On Off Open Battery Ring forward

Battery
Off

Ground
Ringback Battery Open Off On Ground Ground Ringback

Ground
Off
Battery
Flashing Battery Open Off On Ground Ground Flashing

Ground
Off
Battery
On-hook Battery Open Off On Ground Ground On-hook
Disconnect Ground Open On On Open Ground Disconnect

Single Frequency Signals Used in Reverse Battery Tip and Ring Loop Signaling

Calling End Called End
Signal T/R – SF SF – T/R 2600 Hz 2600 Hz T/R – SF SF – T/R Signal
Idle Open Batt-gnd On On Open Batt-gnd Idle
Connect Closure Batt-gnd Off On Closure Batt-gnd Connect
Stop dialing Closure Rev batt-gnd Off Off Closure Rev batt-gnd Stop dialing
Start dialing Closure Batt-gnd Off On Closure Batt-gnd Start dialing
Dial pulsing Open Batt-gnd On On Open Batt-gnd Dial pulsing

Closure

Off
Closure
Off -hook Closure Rev batt-gnd Off Off Closure Rev batt-gnd Off-hook (answer)
Ring forward Open Rev batt-gnd On Off Open Rev batt-gnd Ring forward

Closure
Off
Closure

Ringback Closure Batt-gnd Off On Closure Batt-gnd Ringback

Rev batt-gnd
Off
Rev batt-gnd
Flashing Closure Batt-gnd Off On Closure Batt-gnd Flashing

Rev batt-gnd
Off
Rev batt-gnd
On-hook Closure Batt-gnd Off On Closure Batt-gnd On-hook
Disconnect Open Batt-gnd On On Open Batt-gnd Disconnect

Single Frequency Signals Used for Ringing and Loop-Start Signaling Using Tip and Ring Leads

Call Originating at Central Office End

Signal T/R – SF SF – T/R 2600 Hz 2600 Hz T/R – SF SF – T/R Signal
Idle Gnd-batt Open Off On Gnd-batt Open Idle
Seizure Gnd-batt Open Off On Gnd-batt Open Idle
Ringing Gnd-batt and 20 Hz Open On-off On Gnd-batt and 20 Hz Open Ringing
Off-hook (ring-trip and talk) Gnd-batt Closure Off Off Gnd-batt Closure Off-hook (ring-trip and answer)
On-hook Gnd-batt Closure Off Off Gnd-batt Closure Off-hook
On-hook (hang-up) Gnd-batt Open Off On Gnd-batt Open On-hook (hang-up)

Note: 20 Hz ringing (2 sec on, 4 sec off)

Call Originating at Station End

Signal T/R – SF SF – T/R 2600 Hz 2600 Hz T/R – SF SF – T/R Signal
Idle Open Gnd-batt On Off Open Gnd-batt Idle
Off-hook (seizure) Closure Gnd-batt Off Off Closure Gnd-batt Idle
Start dial Closure Dial tone and gnd-batt Off Off Closure Dial tone and gnd-batt Start dial
Dial pulsing Open-closure Gnd-batt On-off Off Open-closure Gnd-batt Dial pulsing
Waiting answer Closure Audible ring and gnd-batt Off Off Closure Audible ring and gnd-batt Waiting answer
On-hook (talk) Closure Gnd-batt Off Off Closure Gnd-batt Off-hook (answered)
On-hook (hang-up) Open Gnd-batt
Closure On Off Open Gnd-batt On-hook (disconnected)
Off-hook

Single Frequency Signals Used for Ringing and Ground-Start Signaling Using Tip and Ring Leads

Call Originating at Central Office End

Signal T/R – SF SF – T/R 2600 Hz 2600 Hz T/R – SF SF – T/R Signal
Idle Open-batt Batt-batt On On Open-batt
Idle
Seizure Gnd-batt Open On On Gnd-batt
Make-busy
Ringing Gnd-batt and 20 Hz Open On and 20 Hz On Gnd-batt and 20 Hz Open Ringing
Off-hook (ring-trip and talk) Gnd-batt Closure Off Off Gnd-batt Closure Off-hook (ring-trip and answer)
On-hook Gnd-batt Closure On Off Open-batt Closure On-hook
On-hook (hang-up) Gnd-batt Open Off On Gnd-batt Open On-hook (hang-up)

Note: 20 Hz ringing (2 sec on, 4 sec off)

Call Originating at Station End

Signal T/R – SF SF – T/R 2600 Hz 2600 Hz T/R – SF SF – T/R Signal
Idle
Open-batt On On Batt-batt Open-batt Idle
Off-hook (seizure) Ground Open-batt Off On Batt-gnd Open-batt Seizure
Start dial Closure Dial tone and gnd-batt Off Off Closure Dial tone and gnd-batt Start dial
Dial pulsing Open-closure Gnd-batt On-off Off Open-closure Gnd-batt Dial pulsing
Waiting answer Closure Audible ring and gnd-batt Off Off Closure Audible ring and gnd-batt Waiting answer
Off-hook (talk) Closure Gnd-batt Off Off Closure Gnd-batt Off-hook (answered)
On-hook Closure Open-batt On On Batt-batt Open-batt On-hook (disconnected)
On-hook (disconnected)
Closure On Off Open-batt Open-batt On-hook”

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