Telephone Call Support in MOTOTRBO

All MOTOTRBO radios are able to make and receive telephone calls, either via a software appliance or via a hardware-based phone patch. Phone calls are, from the radio's side, semi-duplex in that the radio user still needs to press PTT to speak while the telephone caller needs to wait for the radio user to finish talking (and releases the PTT) before replying.

In all cases, the radio is not connecting into the telephone network itself but rather via a repeater or backend network. This in turn is connected to a phone line, PBX or SIP server and provides telephone interconnectivity.

Radios without a display can only receive phone calls. Radios with a display and limited keypad can make phone calls to pre-programmed telephone numbers. Radios with a full-keypad can however, make phone calls to any number if such numbers are not barred on the system. The currently shipping ION can make phone calls over GSM and/or LTE.

Telephony on Analogue Systems

Almost any analogue two-way radio can make or receive telephone calls using an analogue phone patch. Such hardware has been available on the market for many decades. However with the shift to digital, many of those manufacturers have discontinued production of this hardware or have themselves gone out of business. However, there are still a few manufacturers who produce phone patch hardware - most notably Zetron.

In order to make a phone call, the radio must support DTMF encode. If the radio has no keypad, the user will not be able to dial numbers and so outgoing calls will be limited to what the hardware is able to support. All analogue two way radios will support incoming telephone calls since this is a feature of the repeater and not anything specific to the radio itself. By is nature, a phone call on an analogue system can be heard by all users. If the phone patch hardware supports this, it may be possible to limit the phone call participants by means of PL, DPL or Select-5.

Telephony on Single Site and IP Site Connect Systems

A basic diagram showing how an Analogue Phone Patch is connected to a SLR5500 to provide Digital Telephone Patch service.

There are two known methods for connecting a MOTOTRBO radio system into a phone systemː

• Via a Phone Patch
• Via a SIP Gateway

Digital Phone Patch

Digital Phone Patch is intended to allow a smooth migration to digital while allowing system owners to reuse their existing analogue phone patch hardware.

To make a phone call, a radio user would make a call to the repeater and the radio would send the required DTMF tones. The repeater would present these tones to the analogue phone patch which in turn would place the call on the PABX or PSTN. The analogue phone patch would require a POTS line and would generally be connected to one of the repeaters via the accessory connector.

A CfS License is required to enable Digital Phone Patch functionality in the repeater.

Digital Phone Patch is supported in all MOTOTRBO hardware as of release 1.8 (launched sometime around 2010). Older hardware can be upgraded via CPS to firmware version R01.08.00 or later. to support this.

Known Limitations of Digital Telephone Patch

Digital Phone Patch does not support the following:

• Talkgroup to Phone Call . However, it is possible to call a Talkgroup from a phone.
• Caller Line ID or Phone Number presented to Radio User
• Phone Call Log in Radio (Missed, Answered, Outgoing)
• Radio System Logging of Dialed or Source Phone Number though this can be monitored at a PBX-level.
• Voice Prompts for Radio Users. Some Analogue Phone Patches did
• Custom Ring Tones
• No Transmit Interrupt of a Phone Call
• Encryption on Digital Phone Patch calls.
• Priority Sampling while in a Phone Call
• Emergency Phone Call. But, a radio can Emergency Revert out of a Phone Call.

Configuration

All MOTOTRBO repeaters are capable of supporting telephone interconnect through several models of Analogue Phone Patches.

The Zetron Model 30 Phone Patch, for example, interconnects via the repeater and allows users to initiate and receive land line telephone calls through a connected POTS line. When properly configured, radio users can initiate and answer telephone calls. Through selective signaling, calls from phone callers can be directed to any subscriber or to a specific user. Additionally, access control is also afforded by the Zetron Model 30 Phone Patch.

The connection between a SLR5500 and the phone patch requires a bespoke multi-core shielded cable between the D25 AUX connector on the repeater and screw-terminal block on the Zetron Model 30 Phone Patch. This cable provides the following inputs and outputs to the repeater. The pin numbering is that of a SLR5500 - for a complete listing of SLR5500 pinouts, see the SLR5500 page.

Pin	Function	Configuration	Note
	Transmit Audio	None	300mV nominal, Z=600Ω
	Receive Audio	None	80mV nominal, Z=2kΩ
	PTT	GPIO1, active low	When configured as an input an internal tie-up resistor is in place to sense the line being pulled to ground.
	COR	GPIO1, active high	When configured as an output, an open collector output is presented.
	13,6VDC	None	The SLR5500 provides a 13,6V output on the AUX connector but cannot be safely loaded with more than 1A
	Ground	None

Dialing Radios and Talkgroups via an Analogue Phone Patch

To make a private call to a radio, or a Talkgroup call to multiple radios, a phone caller will need to firstly dial the number associated with the phone patch. If not busy, the phone patch will answer the call and prompt the caller to dial a series of digits. These digits would be presented to and decoded by the repeater which will in turn make the necessary call to the radio(s).

To make a call to a radio with ID 501 on timeslot 1 of a conventional system, the caller would have to dial:

061269576826P18501

Where 061269576826 is the phone number of the Analogue Phone Patch. P usually inserts a 500ms pause between the two adjacent digits. Some phones will use a comma (,) instead of the P. The 1 after the P refers to timeslot 1 on the system. 8 means a private call and 501 is the Radio ID of the called radio. To make a group call to Talkgroup 101 on timeslot 2, the phone caller would have to dial:

061269576826P27101

Here too 061269576826 is the phone number of the Analogue Phone Patch. P (or comma) inserts a 500ms pause. The 2 after the P refers to timeslot 2 on the system. 7 means a talkgroup call and 101 is the ID of the target talkgroup.

To increase the delay between dialing the telephone number and sending the call steering digits, more Ps or commas can be added.

The caller can also manually dial the talkgroup or radio ID. In some cases, the Analogue Phone Patch will prompt the caller to do so.

When dialling the called radio ID, the phone user may try up to three times, after which the system terminates the call automatically if no valid target ID is received. Once the repeater validates the target ID, if the channel is busy, the repeater sounds a busy-waiting tone to on the line and waits for the channel to become idle, before resuming the call setup. While waiting for the channel to become idle, the caller will hear a busy-waiting tone, and can choose to wait or end the call. If the channel does not become idle for a configurable period of time, the repeater ends the call setup and hangs up the call. If the channel is idle or becomes idle before the timer expires, the repeater alerts the called radio user or talkgroup using ringing tones.

A radio user can join a phone call from a phone user while scanning for activities on the phone channel (except in Capacity Plus where scanning is not supported).

Dialing a telephone number from a radio

To make a phone call, the radio user will need to firstly dial the access code for the phone patch, pause to get the dial tone then dial the telephone number. If this were added to the radio contact list, the dialled string would be as follows:

1234#P061269576826

Here 1234# is the access code, P inserts a pause and 061269576826 is the telephone number. In order to make a phone call, the radio user needs to be on the same timeslot as the phone patch.

Telephony on Capacity Plus and Multisite Capacity Plus Systems

Digital Telephone Patch is supported on trunked voice channels of a Capacity Plus system, but is not supported on data revert channels. When a repeater is connected to an Analogue Phone Patch in a Capacity Plus configuration, both timeslots of the repeater can be used for telephone calls. However both timeslots on this repeater operate concurrently (i.e. only one call at a time per repeater) due to hardware limitations.

There can be up to 8 trunked repeaters, therefore 8 Analogue Phone in a Capacity Plus system, thus eight concurrent phone calls can be supported. The radio user does not select which phone channel to use when initiating a phone call because Capacity Plus is a trunked system. The system selects an available phone channel automatically for the call.

When a phone caller initiates the call, they would dial the phone number of the Phone Patch or PBX. They do not specify which channel of the repeater to use. If a PBX is in place, it is recommended to implement call hunting therefore, if any Phone Patch is busy, the PBX will find a free extension to make the radio call.

In order to support phone calls, any DR3000 or MTR3000 repeaters in the system need to be upgraded to R01.08.00 or later.

A CfS License is required to enable Digital Phone Patch functionality in the repeater.

If a radio call is already in progress and a phone caller sets up a new call, the phone gateway repeater will select an idle channel to place the phone call. It could be either slot 1 or slot 2. If both slots on the phone gateway repeater are busy, the caller will hear a busy tone or prompt. An incoming telephone call will not be able to pull radio out of an ongoing radio call, except in the case where the phone caller has dialled All Call. If the incoming telephone call is not All Call, and the target radio is active in a call, the telephone user will hear the busy tone or prompt.

When dialling the called radio ID, the phone user may try up to three times, after which the system terminates the call automatically if no valid target ID is received. Once the repeater validates the target ID, if the channel is busy, the repeater sounds a busy-waiting tone to on the line and waits for the channel to become idle, before resuming the call setup. While waiting for the channel to become idle, the caller will hear a busy-waiting tone, and can choose to wait or end the call. If the channel does not become idle for a configurable period of time, the repeater ends the call setup and hangs up the call. If the channel is idle or becomes idle before the timer expires, the repeater alerts the called radio user or talkgroup using ringing tones.

A radio user can join a phone call from a phone user while scanning for activities on the phone channel (except in Capacity Plus where scanning is not supported).

Dialling Radios and Talkgroups via an Analogue Phone Patch

To make a private call to a radio talkgroup, a phone caller will need to firstly dial the phone patch number. If not busy, the phone patch will answer the call and prompt the caller to dial a series of digits. These digits would be presented to and decoded by the repeater which will in turn make the necessary call to the radio(s).

For example, to make a call to a radio with ID 501 in a Capacity Plus system, the caller would have to dial:

061269576826 wait for the prompt then 8501

Where 061269576826 is the phone number of the Analogue Phone Patch. The 8 means a private call and 501 is the Radio ID of the called radio. To make a group call to talkgroup 101, the phone caller would have to dial:

061269576826 wait for the prompt then 7101

Here too 061269576826 is the phone number of the Analogue Phone Patch. The 7 means a talkgroup call and 101 is the ID of the target talkgroup.

If any of the above telephone numbers were to be stored as a speed-dial in the callers phone, one or more commas (,) or P can be used to insert a delay.

When dialling the called radio ID, the phone user may try up to three times, after which the system terminates the call automatically if no valid target ID is received. Once the repeater validates the target ID, if the channel is busy, the repeater sounds a busy-waiting tone to on the line and waits for the channel to become idle, before resuming the call setup. While waiting for the channel to become idle, the caller will hear a busy-waiting tone, and can choose to wait or end the call. If the channel does not become idle for a configurable period of time, the repeater ends the call setup and hangs up the call. If the channel is idle or becomes idle before the timer expires, the repeater alerts the called radio user or talkgroup using ringing tones.

A radio user can join a phone call from a phone user while scanning for activities on the phone channel (except in Capacity Plus where scanning is not supported).

Known Limitations on Multisite Capacity Plus Systems

Also see Known Limitations of Digital Telephone Patch above.

If there is a Digital Phone Patch only at one RF site in a Multisite Capacity Plus system then in order to make a telephone call, the radio user will need be on (roamed onto) that site. Attempting to make a phone call while on another RF site will fail, even though the two sites are connected. A telephone caller can also only call that radio when it is on the same site as the Analogue Phone Patch.

A telephone caller can call a talkgroup and speak to members, whose radios are on RF sites with no phone patch, as long as the called talkgroup is enabled at those sites and there are free timeslots for that talkgroup call.

Telephony on Capacity Max Systems

Capacity Max does not support Phone Patch like in IPSC and capacity Plus (above). Instead, phone calls are passed through the MNIS VRC Gateway and SIP Gateway or Dispatch Application. There are a number of Application Partners who produce a SIP gateway solution which typically runs on a computer.

Using a SIP Gateway

If a SIP gateway is used in an IP Site Connect, capacity Plus or Multisite Capacity Plus system, this would typically be connected to the repeater via IP. Note that the repeater does not have a SIP client and cannot transcode between AMBE and G711. As far as the radio goes, the SIP gateway acts as a phone patch on the radio network and a SIP client on the telephone network.

Note that the repeater does not have a SIP client and cannot transcode between AMBE and G711.

There are a number of Application Partners who produce a SIP gateway solution which typically runs on a computer. Typically, there would be a number of SIP clients on the gateway to support multiple simultaneous telephone calls. Examples of this include TRBONET SIP-10 and SmartPTT SIP-10 however there are other solutions available.