Recommendation for Enhanced MF Signaling


for the implementation of
Enhanced MF Signaling,
E9-1-1 Tandem to PSAP

NENA Technical Reference

NENA 03-00X Draft 4, March 12, 1997

Recommendation for Enhanced MFSignaling,

E9-1-1 Tandem to E9-1-1 PSAP

Prepared by:

National Emergency NumberAssociation (NENA)

Network Technical Committee

Published by:


Printed in U.S.A.




This Technical Reference ispublished by the National Emergency Number Association (NENA)as a guide and recommendation for designers and manufacturers ofEnhanced 9-1-1 selective routing tandems and customer premisesystems. It is not intended to provide complete designspecifications or parameters, nor to assure the quality ofperformance of such equipment.

NENA reserves the right torevise this Technical Reference for any reason, including but notlimited to, conformity with criteria or standards promulgated byvarious agencies, utilization of advances in the state of thetechnical arts or to reflect changes in the design of equipmentfor services described therein.

It is possible that certainadvances in technology will precede these revisions. Therefore,this Technical Reference should not be the only source ofinformation used to purchase selective routing tandems, customerpremises equipment and/or Feature Group D protocol functionalityfor either. NENA members are urged to contact their localtelephone company representative to ensure compatibility with theTelco network.

The techniques andequipment characteristics disclosed herein may be covered bypatents held by individuals or corporations. No license,expressed or implied, is hereby granted. This document is no tobe construed as a suggestion to any manufacturer to modify itsproducts, nor does this document represent any commitment by NENAor any affiliate thereof to purchase any product whether or notit provides the described characteristics.

This document has beenprepared solely for the voluntary use of E9-1-1 serviceproviders, E9-1-1 equipment vendors, and participating telephonecompanies. It recommends the use of a specific technology forspecific purposes. This document does not automatically excludethe use of any other technologies to provide similar orequivalent services.

By using this document, theuser agrees that NENA will have no liability for anyconsequential, incidental, special, or punitive damages that mayresult.

This document has beendeveloped by the NENA Network Technical Committee. The NENAexecutive board has recommended this document for industryacceptance. Recommendations for change to this document may besubmitted to:

National Emergency NumberAssociation

Attention: ExecutiveDirector

11 South 6th Street

Coshocton, Ohio 43812


1.1 General

This NENA TechnicalReference defines the use of Feature Group D signaling protocolbetween the E9-1-1 selective routing tandem and E9-1-1 customerpremise equipment (CPE).

1.2 Purpose and Scope ofDocument

This Technical Reference isa guide for designers and manufacturers of selective routingtandems and PSAP CPE. It may also be of value to purchasers,maintainers and users of such equipment.

This document describes theuse of Feature Group D (FGD) protocol in place of the protocoldescribed in Bellcore Technical Reference TR-TSY-000350. It doesnot recommend any changes to , or the replacement of, in-placemulti-frequency (MF) signaling used between the E9-1-1 selectiverouting tandem and the E9-1-1 PSAP CPE. Nor does this documentrecommend any other modifications to selective routing tandems orCPE, beyond those necessary to implement the Feature Group Dprotocol.

The purpose of utilizingFeature Group D is to facilitate the delivery of one or twoten-digit ANI transmissions to the PSAP. The protocol supportsboth.

The existing protocol, asdescribed in Bellcore TR-TSY-000350, limits the PSAP to receiving9-1-1 calls from callers in up to four area codes only. Theimplementation of FGD removes that limitation by delivering allten digits of the caller?s telephone number.

FGD also provides for thedelivery of two ten-digit numbers to the PSAP. This capability(delivery of two ten digit numbers) is required to implementPhase 1 of FCC Report and Order 96-264(?), the delivery of awireless 9-1-1 caller?s ten digit callback number plus a tendigit number that identifies the cell/sector through which thecall originated.

1.3 Organization ofDocument

The document is organizedinto four major sections:

Section 1 – Introduction

Section 2 – Call ProgressSignals

Section 3 – TrunkMaintenance Test Calls

Section 4 – Database QueryProtocol

Section 5 – References

1.4 Reason for Reissue

NENA reserves the right tomodify the Technical Reference. Whenever it is reissued, thereason(s) will be provided in this paragraph.


2.1 E9-1-1 PSAP toTandem with 10/20 Digit ANI via Feature Group D Signaling

MF outpulsing is requiredto send ANI to the E9-1-1 PSAP. An idle 9-1-1 trunk to the PSAPis seized and an attempt is made to seize and connect an idle MFtransmitter to the outgoing 9-1-1 trunk. When an MF transmitteris available, it is seized and connected to an E9-1-1 outgoingtrunk to the PSAP. Standard, start-dial timing is done forreceipt of the ANI start signal (approximately 250 +50 mswink signal) from the PSAP CPE. There are several failure modesthat can occur after the E9-1-1 tandem seizes a dedicated E9-1-1outgoing trunk and connects an MF transmitter.

The normal sequence ofevents that occurs after a 9-1-1 trunk seizure is describedbelow. Failure modes are discussed as they are applicable to aparticular sequence.

(Sections 1-3 following arereprinted verbatim from NENA Technical Reference NENA-04-001,Generic Standards for E9-1-1 PSAP Equipment, dated June 20, 1996.Sections 4 and 5 have been taken from NENA-04-001 but modified toaddress the differences and requirements of the FGD typeprotocol.)

1. The E9-1-1 tandem office sends an off-hook signal to the PSAP indicating 9-1-1 trunk seizure.

2. The E9-1-1 tandem office waits 4 to 20 seconds for receipt of the ANI start pulsing wink from the PSAP. The normal call sequence continues if the PSAP returns the outpulsing wink signal. If the start pulsing wink signal is not received within 4 to 20 seconds, the E9-1-1 tandem office puts the trunk on the trunk maintenance list and makes one retry on a different E9-1-1 trunk to the PSAP. In this case, the trunk hunting and the connection phase begin again.

3. When the PSAP recognizes the E9-1-1 trunk seizure, it shall return an ANI start pulsing wink signal (250+50 ms Line Reversal) to the E9-1-1 tandem within 4 seconds. After sending the start pulsing wink signal, if the MF pulses are not received within 4 seconds, or garbled pulses are received, the PSAP completes the call as if an ANI failure has occurred. That is, the CPE shall immediately signal the attendant(s) and return audible ringing to the calling station via the E9-1-1 network. In this case, when the attendant answers, all zeros are displayed on the ANI display. Otherwise, receipt of the start pulsing wink signal typically causes the E9-1-1 tandem office to start MF outpulsing.

4. The MF outpulsing consists of a stream of MF tone pulses, 53 ms to 65 ms duration, separated by silent intervals of 55 ms to 65 ms. The ANI II and DN digits are preceded by a KP digit of 115 ms to 125 ms duration and followed by an STP digit of 55 to 65 ms duration when a single, ten digit ANI is transmitted, or an ST digit of 55 to 65 ms duration when two ten digit numbers are transmitted. (The KP, ST and STP digits are within the family of MF signals.) For transmission of a single, ten digit ANI, the E9-1-1 tandem begins MF outpulsing the ANI information to the PSAP in the form KP II NPA NXX YYYY STP. For transmission of two, ten digit numbers, MF outpulsing begins in the form KP II NPA NXX YYYY (calling party?s number) ST KP NPA NXX YYYY (dialed number or pseudo ANI) ST.

The “II” represents encoded information indicating whether the calling line display device (ANI display) should remain steady or flash, or if the call is a test call. II digits will be used as follows:

II Digit Meaning

40 Steady ANI display

44 Flashing ANI display

48 Test call

If a valid ANI is not available at the E9-1-1 tandem office, a fictitious NPA-NXX-YYYY ANI is sent to the PSAP as either 000-911-0000 or 000-911-0TTT. The digits TTT indicate the E9-1-1 tandem switch Central Office number (also known as ESCO code) associated with the originating office.

000-911-0TTT may be sent due to ANI failures, multi-party or QZ billing lines, and possibly a 9-1-1 call received via a message trunk.

000-911-0000 is sent when an anonymous call is made to a PSAP. An anonymous call is a 7 or 10-digit call (non 9-1-1) to the DN of the PSAP (where applicable).

Note: If an ANI failure occurs between the E9-1-1 tandem office and the PSAP, the digits that may be displayed are 000-000-0000.

5. Upon receipt of the complete ANI information, the PSAP shall signal the attendant(s) and return audible ringing to the calling party. When the call is answered, the PSAP shall disconnect audible ringing, connect the call to the answering attendant, display the calling party?s number on the ANI display, and return an off-hook signal to the E9-1-1 tandem office, indicating that the call has been answered.

If a single, ten digit ANI has been delivered with the call, the E9-1-1 PSAP CPE will display the number on the ANI display and use that number to query the ALI database.

In Phase 1 wireless implementations, when two, ten digit numbers have been delivered, the PSAP CPE will display the calling party?s number on the ANI display, but use the pseudo ANI to query the ALI database.

In Phase 2 wireless implementations, the calling party?s number may be used to query the ALI database, depending upon the configuration of the location determination technology (LDT) interface. In this instance, the pseudo ANI would only be used to query the ALI database in the event the calling party?s number was garbled or not received.

Calls originated from non-service-initialized wireless telephones will not have a calling party number to display. It is also conceivable that multiple calls from non-service-initialized wireless telephones could be received at the PSAP simultaneously. In this event, a “pseudo CPN” may be assigned by the MSC (possibly as a temporary local directory number, or TLDN). This pseudo CPN will be used to tie the x and y coordinates computed by the LDT system to the voice call, but may not be usable as a callback number.

6. After the answer is detected, the E9-1-1 tandem office supervises the call for disconnect and a PSAP transfer request.

3.0 Trunk Maintenance Test Calls

For a PSAP equipped with CPE for ANI display, test calls can be made from the E9-1-1 tandem office using encoded ANI. The PSAP CPE should decode the special ANI as a test call and connect the trunk under test to a test termination facility in the PSAP CPE. Specifically, when KP 48 STP is outpulsed to the PSAP, the E9-1-1 trunk under test should be connected to a permanent busy circuit without answer supervision (no battery reversal) in the PSAP CPE. This allows the E9-1-1 tandem office to verify the integrity of the circuit using the trunk diagnostic program. The test call sequence is listed in the following three steps:

1. After seizing the selected idle trunk and receiving the wink start signal prior to time-out, the E9-1-1 tandem office outpulses KP 48 STP to the PSAP.

2. The PSAP should interpret the digits 4 and 8 as a maintenance test call and connect the incoming E9-1-1 trunk to a permanent busy tone (continuous 60-ipm, tone) without answer supervision (normal battery polarity). The tone should be returned to the E9-1-1 tandem office within 20 seconds after receipt of the wink start pulse, otherwise, the E9-1-1 tandem office would consider the trunk test a failure.

3. Approximately 5 seconds after receiving the 60-ipm tone, the E9-1-1 tandem office disconnects and idles the trunk under test. It is not necessary for the PSAP to do any timing for a maintenance call, but merely react to the seizure and disconnect from the E9-1-1 tandem office.


4.1 Change to Query Protocol

The change to the ANI delivery protocol will necessitate a corresponding change in the ALI database query protocol. In short, the NPD digit will be replaced by the three digit NPA. No other modifications are envisioned at this time.

The resulting protocol will be as follows:




No modifications are required for ACK?s, NAK?s, heartbeats or ALI text messages sent from the ALI/DMS to the PSAP.


5.1 Technical References

Document Number | Description |Issue Date

TR-TSY-000350 Bellcore. E9-1-1 Public Safety Answering Point: Issue 1, 1987

Interface Between a 1/1AESS Switch and

Customer Premise Equipment

NENA-04-001 NENA. Generic Standards for E9-1-1 PSAP Issue 1, 1996

N/A E9-1-1 ALI Multiplexer System 1988

(ALI/DMS) PSAP -Node Interface

Specification (AT&T)