A fire or EMS agency that moves its voice traffic onto a P25 trunked system discovers, usually in the first planning meeting, that the two-tone pagers on the belts of its members cannot hear the new channel. The choice of what replaces them is a policy decision about who gets woken and how dispatch will know it worked, and the hardware only sets the limits. This piece explains why analog tones do not survive a digital vocoder, what the P25 standard itself provides for alerting, where Motorola Solutions and L3Harris differ, and what a chief who already owns an L3Harris Phase 2 system should ask before writing the protocol.

Why the Minitor goes quiet: two-tone paging, the vocoder, and a pager that cannot demodulate C4FM

Two-tone sequential paging works by sending two audio tones one after the other on an analog FM channel, and a pager programmed for that pair opens its speaker when it hears both in order. Motorola’s trade name for its version is Quick Call II, and the Minitor line of pagers decodes it, as do pagers and encoders from several other makers. Genave, which sells tone encoders, publishes the timing as a one-second first tone followed immediately by a three-second second tone with no gap between them, and Genave describes the all-call as a single continuous tone lasting eight seconds. The scheme depends on the receiver recovering the exact audio frequencies, which an analog FM discriminator does because the tones ride the carrier as ordinary audio. The site’s earlier piece on the pager era covers how the format came to dominate volunteer alerting.

A P25 channel carries no audio in that sense. The transmitting radio samples the microphone, runs the samples through a vocoder, and sends the resulting bits as a digital modulation, which on Phase 1 is C4FM at 9600 bits per second in a 12.5 kHz channel. The P25 vocoder description, TIA-102.BABA, specifies two rates from the same vendor, Digital Voice Systems Inc.: the full-rate IMBE vocoder used on Phase 1 and the half-rate AMBE+2 vocoder used on Phase 2 traffic channels. A vocoder of this family models the speech as a set of parameters (pitch, voicing decisions, and spectral amplitudes in a number of bands) and sends those parameters, so the waveform itself is never transmitted. That is why a steady pure tone, which is nothing like speech, comes out of a naive voice encoder distorted and shifted in level.

The standard does make some provision for tones, and only in the newer of the two vocoder modes. The half-rate vocoder addendum, TIA-102.BABA-1, published in 2009 for Phase 2, defines tone frames: when the encoder detects a single tone, a DTMF digit, a Knox tone or a call-progress tone, it sends a frame carrying a tone index and an amplitude in place of speech parameters, and the receiving vocoder synthesizes the tone from those two values. Single tones are indexed in steps of 31.25 Hz, so a tone that falls between two steps is regenerated at the nearest one. The original IMBE description defines no tone frame, and the addendum gives guidance for approximating a half-rate tone frame in a full-rate voice frame. Motorola’s tone feature, described below, also works on Phase 1 channels, which indicates that current vocoder implementations carry tones in full-rate operation by means the original description did not define, so the chief should ask which vocoder generation each radio and console in the fleet carries. I found no statement from TIA, the Project 25 Technology Interest Group or either radio vendor on how reliably a two-tone page survives that process, so its reliability is something an agency has to test on its own system.

The tone-frame mechanism does not help the pager on the belt. A Minitor-type pager is an analog FM receiver with a tone decoder behind it, and if it is tuned to a P25 channel it hears the digital carrier as noise and never sees two clean tones. The tone-frame mechanism is a way for one vocoder to tell another vocoder to regenerate a tone, so it only works between two devices that both implement the digital side. The practical statement for a chief is that nothing an agency can do at the dispatch console will make an analog pager decode a digital channel, and the real choices are to keep an analog channel for the pagers or to buy devices that decode P25, with alerting outside the radio system as a supplement to either.

What TIA-102 gives every radio: Call Alert, announcement groups, all-call, status, emergency alarm, and the Phase 2 differences

In the TIA-102 suite the group voice call is the core service, and Call Alert (also called Unit Page), the Announcement Group Call, the System Call, Emergency Alarm, Status Update, Status Query and the Short Message are supplementary or optional services that a manufacturer may or may not implement. The distinction matters because each of these is defined over the air, so any vendor that implements it must do so the same way, but no vendor is obliged to implement it on a given radio or console, and some sell it as a licensed feature. The TIA document on supplementary data over the Inter-RF Subsystem Interface lists Emergency Alarm, Call Alert, Short Message, Status Query and Status Update among the services that can cross between two vendors’ systems, which matters in a region where a Motorola system and an L3Harris system are joined.

Each service does the following. A Call Alert is a signaling message addressed to one radio by its unit identifier, which causes that radio to sound an alert and, in the trunked procedures, to return an acknowledgement through the system to whoever sent it. It carries no voice, so Call Alert is a way to ring one device and learn that it rang. A group voice call on an alerting talkgroup is the ordinary mechanism everyone already uses, with the talkgroup chosen so that the stations and apparatus to be alerted are affiliated to it. An Announcement Group Call is a voice call addressed to an announcement group, which the system maps to several ordinary talkgroups so that every radio on any of them hears the call at the same moment. The System Call is the same idea extended to every radio on the system. Status Update lets a radio send one of a set of predefined status codes to dispatch, Status Query lets dispatch ask for one, and Short Message lets a radio send a short predefined message. Emergency Alarm is a control-channel message that marks the sending radio as in emergency, and addenda to the trunking control channel messages standard, TIA-102.AABC, have added flags for an alarm raised by a vehicle sensor or activated remotely. Dynamic regrouping lets the system move a radio to a different talkgroup over the air, which changes what the radio is listening to instead of ringing it. The Statement of P25 User Needs that CISA published in March 2025 lists announcement group calls and dynamic regrouping as trunking features, so an agency still dispatching fire on P25 conventional channels does not have them.

Phase 2 changes less of this than a chief might expect, because the alerting functions ride the control channel, and on most Phase 2 systems the control channel is the same FDMA channel that Phase 1 uses. The TIA document describing the Phase 2 two-slot TDMA media access control layer states that trunking control functions are conveyed through a Phase 1 FDMA control channel, with the voice carried on a two-slot TDMA traffic channel. An Urgent Communications explainer on Phase 2 TDMA says the design uses the existing Phase 1 FDMA control channel with extensions that let the system learn each radio’s TDMA and vocoder capabilities, so that one control channel manages both Phase 1 and Phase 2 radios on the same site. A Call Alert, a Status Update, an Emergency Alarm and a channel grant are all control channel traffic, so they work the same on a Phase 2 system as on a Phase 1 system. One qualification applies to newer systems: TIA later standardized a TDMA control channel, and a Project 25 Technology Interest Group white paper from September 2017 explains that it supports the same functions as the FDMA control channel but serves only radios built with TDMA control channel capability. L3Harris lists a P25 TDMA control channel as a separately coded option on its XL radios, so an administrator who has enabled one should say which pagers and radios in the fleet can use it.

What does change is the voice path and therefore the vocoder. A Phase 2 trunked voice call runs on a TDMA traffic channel using the half-rate AMBE+2 vocoder, while Phase 1 conventional and Phase 1 trunked calls use the full-rate IMBE vocoder, and a radio that is Phase 1 only cannot take a Phase 2 traffic channel at all. For an alerting talkgroup or an announcement group that means any voice pager or radio meant to hear the dispatch must be Phase 2 capable if the system assigns that talkgroup to TDMA channels, and any tone-over-P25 feature must work through the half-rate vocoder. Phase 2 is a trunking technology, so a P25 conventional channel uses the Phase 1 FDMA air interface. Motorola documents a behavior it calls Dynamic Dual Mode, in which its system moves a talkgroup back to an FDMA channel when a Phase 1-only radio joins it, and the L3Harris administrator should say how the VIDA system handles the same case. Whether a system assigns a particular talkgroup to FDMA or TDMA is a configuration question for the administrator, and it is the first thing to settle before buying pagers.

One engine, one house, or everybody: selecting targets and the sequential-versus-simultaneous clock

The analog model gave each station, and sometimes each piece of apparatus, its own tone pair, and the dispatcher sent the pairs for the units on the assignment one after another before reading the call. The P25 model offers four addressing levels, and a single device can be reached by Call Alert to its unit ID. A single station or apparatus can be reached by a talkgroup assigned to it alone, by a Call Alert to each radio in it, or by a tone-over-P25 feature if the devices support one. A group of stations is reached by an announcement group that maps to their talkgroups, or by a talkgroup all of them monitor. The whole department is reached by a department-wide announcement group or by a System Call. Most agencies use a mix, with a dispatch talkgroup that every member monitors for awareness and a narrower mechanism for the units assigned.

The policy trade-off shows most clearly in the structure-fire alert that wakes the whole department at two in the morning. A department-wide announcement for every working fire gives every member the situational picture, including the off-duty chief officer and the station that may be moved up, and it has the side effect of waking members who will not respond and whose sleep the agency ought to protect. A narrower alert to the assigned units only keeps the rest asleep and leaves them to learn of the fire from the next day’s reports, and it also removes the informal check in which a neighboring station notices that the assigned company has not acknowledged. The tools for managing this are a department-wide group that members may mute by policy at night and a Call Alert or station alerting activation for the assigned units that cannot be muted. The site’s earlier article on station alerting goes into the ergonomics of waking crews.

The analog and digital models differ most in timing, and the arithmetic is simple enough to do in the open. On the one-and-three timing that Genave publishes, which Motorola’s service documentation for its SABER radios also gives, each tone set takes four seconds before any voice is sent. A first-alarm assignment with six units, each with its own tone set, is 24 seconds of tones before the voice, and real dispatch practice adds a short gap between sets and often a repeat. Motorola’s documentation describes an eight-second tone for its super group call format, and Genave describes the all-call as a continuous eight-second tone; a long tone that opens every pager at once shortens the sequence for a general alarm, at the cost of waking every station for every call that uses it.

In P25 trunking the control channel runs continuously at 9600 bits per second, and a Call Alert is a brief exchange of messages on it, while an announcement group call is a single channel grant that every affiliated radio follows at once. I am not going to give a figure for how long a Call Alert takes end to end, because I could not find a published measurement for either vendor’s system and the number depends on control channel loading and on where the target radio is, including whether it is already on a voice channel. The closest published measurements are for voice access rather than alerting: in 2019 the Public Safety Communications Research program at NIST measured the time from pressing push-to-talk to intelligible audio at a receiving radio at about 1.0 second on a Phase 1 trunked test system and about 1.27 seconds on a Phase 2 trunked system, against about 0.29 seconds radio to radio in direct mode. Those are laboratory figures for one configuration, useful for scale and no promise about any particular system. The mechanism is what the chief needs to understand: a sequence of Call Alerts is still sequential, one message exchange per radio, while an announcement group call reaches everyone in the time it takes the system to assign one traffic channel. For a department that wants fifty radios to open at once, the announcement group or the alerting talkgroup is the mechanism built for the job, and a tone sequence transmitted over P25 inherits the same four seconds per tone set that it had on analog, because the tone timing is a property of the pager format rather than of the channel.

Night modes: muted radios, timed unmute, and which behaviors are standard versus product features

A radio left unmuted on a busy dispatch talkgroup is the simplest arrangement, and the trouble of sleeping next to one is the reason the analog pager, silent until its own tones arrived, was well liked. Nothing in the P25 standard describes a muted-until-selected behavior or a timed unmute, since the standard defines what goes over the air and leaves how a radio treats its own speaker to the manufacturer, so every behavior in this section is a product feature and the vendor’s own documents are the source for it.

Motorola’s published description is the most explicit I found. In a March 2015 press release for the IWCE trade show, Motorola Solutions announced what it called Digital Tone Signaling Software, which it said would let APX radios serve as a digital pager on conventional and trunked P25 systems, so that a firefighter could use the radio by day and as a pager at night, muting it to rest and relying on the paging feature to unmute it when the agency’s quick call tones arrived over the digital system. The APX NEXT XN data sheet lists digital tone signaling as a footnoted option, and APX user guides carry a section on Quick Call II for ASTRO P25 digital trunking and conventional operation. APX radios also have a mode Motorola calls In-Call User Alert, which its user guides describe as keeping the radio muted to talkgroup and dispatch calls while group and individual pages, and individual radio-to-radio calls, still unmute it. What the published material does not say, and what the chief has to ask, is how long the radio stays unmuted after a tone decode or a page, whether that interval is programmable, whether the user can re-mute by hand, and whether the behavior is identical on APX mobiles and portables.

Unication’s published page for its G-series voice pagers lists support for analog two-tone conventional, P25 conventional, and P25 trunked Phase I and Phase II, and lists four alerting configurations: analog two-tone, talkgroup ID, what it calls QCII over P25, and Call Alert. It also lists Selective, Monitor and Scan as function modes for analog two-tone, which correspond to the familiar pager behaviors of silent until paged, always open, and scanning between channels. The Unication page does not describe the unmute interval or re-mute behavior, and I would ask the vendor for those figures before writing them into a protocol. A note on the RadioReference thread about tone decoding on L3Harris XL radios also applies to any scanning device: a user with long experience warned that a radio scanning several channels can miss the start of the first tone and fail to decode, so a device meant to be alerted by tones should sit on the alerting channel rather than scan.

L3Harris documents its radios’ behavior in the operator’s manual for the XL Converge portables, revision AG of September 2026, and in its XL series software features catalog of March 2026. On analog conventional channels the radios support what L3Harris calls Type 99, its name for two-tone sequential signaling: the radio stays muted until it detects its tone sequence, sounds an alert, and opens the speaker for the message, and an Auto Reset option the agency can program turns Type 99 back on 30 seconds later, so the radio goes quiet again without anyone touching it. For P25 trunked systems the catalog lists P25T Two-Tone Paging as an optional feature on every current XL model, described as enabling two-tone paging signals over P25 trunked radio systems, but neither the catalog nor the manual describes how a radio with that feature unmutes or re-mutes. The manual describes a received Call Alert as ringing continuously, with the caller’s name or unit ID on the display, until the user presses push-to-talk, clears it, changes group or turns the radio off, and it describes a programmable mute button that silences all audio until it is pressed again or an individual call arrives. The questions for the L3Harris representative are what a radio with P25T Two-Tone Paging does after it decodes its tones, how long it stays open, whether the feature works on Phase 2 TDMA talkgroups through the half-rate vocoder, and whether a Call Alert or an individual call overrides a radio muted for the night on both the portables and the XL Onboard mobiles. Mobiles differ from portables in practice because a mobile in the apparatus bay is usually left on and unmuted on the dispatch talkgroup, while the portable goes home on a belt or a nightstand, so the night mode question is mostly a portable and pager question.

Did they get it: acknowledgements, status messages, and what a chief officer can actually see

An analog pager gave dispatch no signal that it had fired. Dispatch learned that a station had received its page when a unit answered by voice, and a station that did not answer within the agency’s time limit got a second page and then a phone call. P25 adds some signaling that closes part of that gap, and it is worth being exact about what each piece does and does not show. The trunked Call Alert carries an acknowledgement, so the originating console or radio can learn that the target radio received the alert message; that acknowledgement is generated by the radio itself, and it says nothing about whether the speaker was audible in the room or whether a firefighter woke up. A Status Update from a radio, or a response to a Status Query, is a code the radio sends, and if the agency programs a status button labeled “received” or “en route” the firefighter can press it and the console can display it, which does come from a person.

What the console shows for each of these is console-specific, and here the published standards stop helping. The standard defines the Call Alert acknowledgement and the Status Update message over the air; how a Motorola MCC 7500E or an L3Harris Symphony console displays an acknowledgement, whether it logs the time, whether it raises an alarm when an expected acknowledgement does not arrive, and whether it passes the event to CAD are questions for the console documentation and the system administrator. L3Harris’s Symphony training material shows radio status messages in a panel listing the unit, the time and the status, and I found nothing in it describing a Call Alert acknowledgement display. On the radio side, Motorola’s APX user guides say the sending radio shows Ack received when the target acknowledges and No acknowledge when it does not. A station alerting system, meaning the purpose-built equipment in the station that is fed by CAD over IP or triggered by radio, generally confirms its own activation: Honeywell’s documentation for the US Digital Designs Phoenix G2 station controller says it returns an acknowledgment to the gateway at the dispatch center, and Motorola says its MACH Alert product gives dispatch positive confirmation that each station was alerted. That confirmation is about the station controller receiving the activation and says nothing about the crew.

A battalion chief looking at a mobile radio sees the talkgroup activity and any Call Alert addressed to that mobile, and nothing else. The radio alone cannot show that Station 3 acknowledged or that the station alerting controller at Station 5 failed to activate, because none of those events are addressed to the chief’s radio, and a portable shows the same. L3Harris’s push-to-talk application, renamed from BeOn to XL Virtual in 2024, puts a phone on the radio system, but the XL Converge operator’s manual lists Call Alert and status messages among the features not available over XL Virtual, so it does not fill the gap. The responder apps many volunteer agencies already use come closer: IamResponding, for one, publishes that chiefs and dispatchers can see who is responding, their qualifications, when they responded and whether they are going to the station or the scene. That is a human response carried by a phone app outside the radio system, so a chief who wants to see in the field who got up should look to the CAD, the station alerting system or the responder app before the radio.

The gap that remains under any of these arrangements is the one between a device acknowledging and a person responding, and agencies that have thought this through write the acknowledgement into policy as a human act, such as a voice acknowledgement on the dispatch talkgroup or a status button press within a set time, while treating the Call Alert acknowledgement and the station controller confirmation as evidence that the signaling worked.

How each option fails: station alerting, Call Alert, alert talkgroups, a retained analog channel, and the phone

A dedicated station alerting system fed by CAD over an IP network is the most capable option, and it depends on the CAD, the network path to each station, the station controller, and the station’s power. Its usual backup is the trunked radio, with the alerting talkgroup fed to the station’s speakers through a radio in the station, which means the backup depends on someone having tested the radio path recently. Earlier editions of NFPA 1221, now consolidated into NFPA 1225, required a jurisdiction receiving 730 or more alarms a year to have separate primary and secondary dispatch circuits, with the failure of any part of the primary not affecting the secondary, and that requirement is the basis for the common design of IP first and radio second. The failure mode worth planning for is the partial one, in which CAD sends the activation, the controller at one station does not respond, and dispatch does not notice because the other stations did, which is the main reliability argument for buying a system that confirms activation back to dispatch.

Call Alert fails when the target radio is off, out of coverage, on a different site in a way the system cannot resolve, or already on a voice call in a mode where the alert is deferred, and it fails silently from the dispatcher’s point of view unless the console shows the missing acknowledgement. It also fails in volume, because a dispatcher sending one Call Alert per radio to a large department is doing the analog era’s sequential work on a keyboard. Its reliability advantage is that the acknowledgement exists at all, so an agency can write a rule that an unacknowledged Call Alert is re-sent once and then followed by voice. An alerting talkgroup or announcement group fails when the system is down or a radio is unaffiliated or out of coverage, and it fails just as completely when the radio is muted and nothing unmutes it, and in either case it gives dispatch no signal that any particular radio heard it, so it reaches the most radios with one message while giving dispatch no confirmation from any of them.

Keeping an analog paging channel for the existing pagers is the option that most volunteer-heavy agencies choose during a transition, and it is reliable in the way the pager era was reliable, with pagers that need nothing from the trunked system and a failure mode that is mostly the single transmitter site and its backup power. It carries a cost the chief should state plainly: the analog channel has to be licensed and maintained and the dispatch console has to encode tones to it alongside the P25 traffic, while the voice the pagers hear is a second copy of the dispatch that can drift out of step with what the trunked talkgroup carries unless the console is patched or the dispatcher reads the call twice. Part of the reason the format lasted so long is that this failure mode is simple and well understood.

Cellular and app-based alerting, whether a commercial responder app or a vendor’s push-to-talk application, is a supplement with its own failure modes: the carrier network, the phone’s battery and settings, the do-not-disturb mode the member turned on at bedtime, and the app’s own server. It reaches members who are away from any radio and can carry text and maps that a voice page cannot, though it is unsuitable as the primary mechanism for a crew that must leave the station in under a minute, and any protocol that includes it should say that the radio or the station alerting system is the alert of record.

Motorola Solutions and L3Harris compared

The standard functions are the same on both vendors’ systems, and that should be said first because it answers the question a chief most often asks. Call Alert, group calls, announcement group calls, System Call, Status Update, Status Query and Emergency Alarm are defined over the air by TIA-102, and a radio from either vendor that implements them sends and receives the same messages on the control channel. An L3Harris Phase 2 system will deliver a Call Alert to a Motorola APX radio registered on it in the same way it would to an L3Harris XL radio, provided both the system and the radio have the feature enabled, and the ISSI supplementary data standard extends the same functions across a link between two vendors’ systems. The Department of Homeland Security notes on its P25 Compliance Assessment Program equipment list that a listed product does not necessarily support every P25 feature, so the chief should read the test report for the specific radio instead of inferring support from the listing.

The difference begins with tones carried over P25. Motorola has published, in a 2015 press release, its APX user guides and the APX NEXT XN data sheet, a tone signaling feature that lets an APX radio decode quick call tones sent over a P25 system and unmute. L3Harris lists P25T Two-Tone Paging as an optional licensed feature on its current XL radios, and in a December 2021 flyer it presented Unication’s G-series pagers as its voice paging solution for L3Harris P25 systems, with two-tone over P25 among their alerting modes. Both depend on the receiving device implementing the same tone mechanism as the sending console, and I found no published test showing that a Motorola radio decodes tones sent through an L3Harris console and system, or the reverse. For an L3Harris owner with a mixed fleet this is the central question, and the exact question to put to both vendors is which devices on this specific system will decode a tone sequence sent from this specific console over a Phase 2 traffic channel, and whether that has been tested on the system rather than in a lab.

The two vendors document their consoles differently. Motorola’s current console for ASTRO 25 systems is the MCC 7500E, the earlier MCC 7500 now being listed by Motorola as discontinued. A 2015 Motorola price sheet listed an integrated tone paging encoder among the MCC 7500’s basic software features, covering Quick Call II formats, group and stacked pages and quick-page buttons; I could not confirm that the 7500E carries the same list, and its data sheet mentions an external paging encoder port. L3Harris’s training material for the Symphony console describes single, stacked, One Touch and composite paging, in which one touch can send a page or a stacked page, open a simultaneous selection of up to fifteen talkgroups, units or channels, and send an alert tone. The same material says Symphony’s analog pages travel as ordinary calls with the tones inside the call, while its digital pages go to a single unit and carry only DTMF or Knox tones. Whether a given position at a given center can do all of this, whether it originates a Call Alert, and whether it shows the acknowledgement are configuration and licensing questions that the published documents do not settle.

The two vendors’ arrangements for station alerting differ more than anything else in this comparison. Motorola sells its own station alerting product, MACH Alert, which it describes as integrating with its MCC consoles, using dual alerting paths and returning per-station confirmation to dispatch; Houston and New Orleans are among the agencies with published agreements for it. L3Harris does not sell its own. Its Mission Critical Alliance names Zetron’s MAX Fire Station Alerting as the partner product, and Zetron said when it joined the alliance in 2019 that the integration delivers alerts, text-to-speech announcements, station controls and alert confirmations from L3Harris consoles and systems. Independent products such as the US Digital Designs Phoenix G2, owned by Honeywell since January 2022, Westnet First-In and Purvis are driven by CAD and use the radio system as a trigger or a backup path, and Honeywell lists Motorola and Harris among the radio makers it integrates with. For an L3Harris owner the practical consequence is that station alerting will come from a partner or an independent vendor, and the chief should ask that vendor for a written list of the CAD and console integrations it supports on a VIDA system.

The pager offerings are easy to state. Motorola’s own pagers, the Minitor VI and the Minitor 7 introduced in 2024, are analog two-tone receivers, and I found no Motorola-branded P25 pager. L3Harris does not sell a pager either, and the device both vendors’ customers buy when they want a P25 pager is the Unication G-series, which the manufacturer lists as supporting P25 trunked Phase I and Phase II with talkgroup, Call Alert and two-tone-over-P25 alerting; the G4 appears on the DHS compliance assessment list as a Phase 1 trunked subscriber. That listing does not cover Phase 2 operation, so the agency should ask Unication for a Phase 2 test report rather than rely on the product page. The pagers are receive-only, so they cannot acknowledge a Call Alert. Whether the two-tone-over-P25 mode decodes the encoding that the agency’s console sends is something to test on the agency’s own system before buying a fleet, because a pager that alerts on talkgroup activity or a Call Alert works on any compliant system while one that depends on a particular tone encoding may not.

Configuration of alert and unmute behavior is product-specific on both sides, as the night modes section describes, and acknowledgement and status handling is standard over the air and product-specific on the console, so the interoperability limit in a mixed fleet lies in the tone-over-P25 features and in any console behavior that depends on the vendor’s own data between console and radio. On licensing, L3Harris publishes more than Motorola does. Its March 2026 software features catalog lists P25 Phase 2 trunking, the TDMA control channel, multi-system scanning and two-tone paging as separately coded options on XL radios, and a 2020 L3Harris price list for the State of Mississippi showed the Phase 2 feature at $250 list per radio; current prices are not published. I found no published Motorola price list for the equivalent APX options. The chief should ask both vendors for the written option price per radio, per pager and per console position, and for the renewal terms.

The questions an L3Harris Phase 2 owner should put to the vendor and the system administrator before choosing a protocol are these.

• Which of Call Alert, announcement group call, System Call, Status Update and Status Query are enabled on this system today, and which radios and console positions have them licensed?
• Are the fire dispatch and alerting talkgroups assigned to FDMA or TDMA traffic channels, and will every pager and radio that must hear them operate on a Phase 2 channel?
• Does this system use the FDMA control channel or the TDMA control channel, and can every pager and radio in the fleet operate on it?
• Which XL portables and mobiles in the fleet have P25T Two-Tone Paging licensed, what does a radio with it do after it decodes its tones, how long does it stay open, and has that been tested on this system’s Phase 2 talkgroups?
• Does the Symphony console display the Call Alert acknowledgement, log it with a time, and pass it to the CAD, and what does the dispatcher see when an acknowledgement does not arrive?
• Which station alerting products are integrated with this CAD and this console, and does each confirm activation back to CAD?
• If Unication pagers are proposed, which of their alerting modes has been tested against the console on this system, and which of those modes depend on a tone encoding rather than on talkgroup or Call Alert signaling?
• What is the written price per radio, per pager and per console position for every option on this list, and what are the renewal terms?

Briefing the crews: what to tell firefighters and EMTs about a new alerting protocol

The members who will live with the protocol need the same honesty the chief needed from the vendor, and they need it in the order they will use it. The first thing to tell them is what changes in their hands: which device will ring for an assigned call, which will carry awareness traffic, what the device does when it rings, and what they are expected to do within how many seconds. If the plan uses a dispatch talkgroup for awareness and a Call Alert or station alerting activation for the assignment, say so in those words, and say which of the two they are allowed to mute at night. A member who understands that the awareness talkgroup may be muted but the assignment path cannot be will make the right choice at bedtime.

The second thing is why the protocol was chosen, stated as the trade-off it was. If the department kept an analog paging channel, the members should hear that it was kept because their pagers cannot decode the new system and because the analog path fails simply, and they should hear the cost, which is that the dispatcher now sends the call twice. If the department bought P25 pagers, they should hear which alerting mode those pagers use and that the mode was tested on the agency’s own system on a stated date. A member who knows the reasoning can describe a failure in terms the system administrator can act on.

The third thing is how it was tested and what happens when it fails. The briefing should describe the test, with the number of stations and devices, the time of day and the results, and it should name the failure procedure in one sentence per failure: if the station alerting system does not activate, dispatch re-alerts by radio; if a Call Alert is not acknowledged, dispatch sends it once more and then calls the station; if the trunked system is down, dispatch uses the analog channel or the phone tree; if a member’s device never rings for an assigned call, the member reports it that shift on a specific form to a specific person. The test should therefore include each failure procedure as well as the normal path, so that every one of those sentences is true when the chief says it.

The last thing is the expectation at night. If the protocol says a member on the duty roster keeps the portable unmuted on the assignment talkgroup, or keeps the pager in selective mode within reach, that expectation should be written down and attached to the roster and read aloud at the briefing, so that a missed call at three in the morning is judged against a written expectation. The chief should also say what the agency will do with the acknowledgement data it now has, since members will notice that dispatch can see which radios acknowledged, and should state that the data is used to find failed devices and dead spots.

What to do at your agency

• The radio system administrator should produce a one-page written list this month of which standard P25 signaling services are enabled on the system, which radios in the fire and EMS fleet have each one licensed, and which console positions can originate each one, and the chief should file that list with the alerting protocol.
• The system administrator should confirm in writing, from the system’s configuration rather than from memory, whether each fire dispatch and alerting talkgroup is assigned to FDMA or TDMA traffic channels, and should list every pager and radio model in the fleet that cannot operate on a TDMA channel.
• The communications officer should run a dated night-shift test of the current alerting path at every station, recording for each station the time the activation was sent, the time it was heard, and whether any acknowledgement reached the dispatcher.
• The communications officer should put the vendor question list from this article in front of the L3Harris representative and the system administrator at the next scheduled system users meeting, and should ask for written answers rather than verbal ones.
• The training officer should write one paragraph into the existing communications SOP stating which device is the alert of record for an assigned call, which traffic members may mute at night, and what a member does the same shift when an assigned-call alert does not reach their device.
• The dispatch center manager should add one paragraph to the existing dispatch SOP naming the re-alert procedure for each failure: station alerting controller not confirming, Call Alert not acknowledged, and trunked system unavailable, with the time limit for each step.
• If the agency proposes to buy P25 voice pagers, the communications officer should borrow or buy two units first and test each advertised alerting mode against the agency’s own console on the agency’s own system, recording which modes worked, before any fleet order is placed.

Takeaways

• An analog two-tone pager is an FM receiver with a tone decoder, and it cannot demodulate a P25 channel, so no console setting will make the existing pagers work on the trunked system.
• The P25 vocoders model speech as parameters rather than carrying audio; the half-rate addendum adds tone frames that regenerate a tone at the receiving vocoder in 31.25 Hz steps, and that only works between two devices that both implement it.
• Call Alert, announcement group calls, System Call, Status Update, Status Query and Emergency Alarm are defined by TIA-102 as optional services, which means they interoperate across vendors but are not guaranteed to be present or licensed on any given radio or console.
• Most Phase 2 systems keep the Phase 1 FDMA control channel, so the signaling-based alerting functions work the same on both phases; a system running the newer TDMA control channel serves only radios built for it, and the voice path moves to two-slot TDMA with the half-rate vocoder and excludes Phase 1-only devices.
• On the one-and-three-second tone timing that Genave publishes, each analog tone set costs four seconds before any voice, while an announcement group call reaches every affiliated radio with one channel grant, and a Call Alert is one message exchange per radio.
• Muted-until-paged, timed unmute and manual re-mute are product features rather than standard behaviors: Motorola documents In-Call User Alert and digital tone signaling on APX radios, L3Harris documents Type 99 with a 30-second Auto Reset on analog conventional channels and sells P25T Two-Tone Paging for trunked use, and I found neither vendor’s published figure for how long a radio stays open after a page on P25.
• A Call Alert acknowledgement and a station alerting confirmation prove that a device received the signal and prove nothing about a person, so the human acknowledgement has to be written into policy separately.
• Published accounts from Monroe County, Michigan, Daviess County, Kentucky, and Franklin County, Massachusetts, describe P25 pager transitions and their coverage problems, but none measures turnout time and I found none that concerns an L3Harris Phase 2 system, so an agency planning a transition should run and record its own test.