Repeater audio priority

Q. In the SLR5500 repeater, there are two fields within the Accessories section of the software: TX audio priority and Repeater Audio priority. Using these one assumes that you can make both routes of audio (and PTT input) either equal, priority towards the internal repeater path, or priority towards the external TX audio and PTT input. 

We connect our systems to external communications systems, so use the TX audio input plus external PTT input often, as well as the normal repeat path. Firstly are you able to explain in more detail what the various levels of priority within each dropdown field for these settings actually changes within the repeater? Available values are 0,1,2,3 for each field, yet there can still only really be 3 scenarios. Equal, TX audio lower than Repeater audio, or vice versa. 

Our end goal is to allow fully equal priority to both repeater audio path and TX audio path, so that users receiving the repeaters transmission receive a mix of both the repeated audio (radio to radio users) and the TX audio (external incoming audio to radio users), regardless of whether the repeat path PTT, the external PTT, or a combination of both PTT triggers is present.

This above scenario does not seem possible, so I would love to get your thoughts on this.

A. When operating in analogue mode, the SLR5500 can be configured to accept voice and PTT from either the (RF) receiver or an input from the accessory connector. The accessory connector input would typically come from some form of peripheral equipment that needs to transmit and receive via the repeater (e.g. a tone remote adapter).

The SLR8000 has two additional input paths: one from the front panel and one via wireline. The front panel refers to the microphone (engineering handset) plugged in on the front. Wireline refers to same coming in on the wireline card using either tone or DC remote control. These two do not exist on the SLR5500 since it has neither of these.

This feature/function is not really described very well anywhere but my understanding is as follows:

These settings can be found in the repeater codeplug, in the Accessories set, under General.

The purpose of this group of settings is to allow the repeater to decide which audio source to give priority to, if it receives a trigger from both (or all) at the same time (i.e. within a few milliseconds of each other). This is necessary because radio users will only want to hear voice from one of these sources at a time.

With the exception of Disable Repeat Path, all of the above settings can be set to a whole number between 0 and 3. Setting any one of these to 3 means that source has the highest priority. All of these settings are applicable in analogue mode only.

Let's assume a SLR5500 is connected to a RoIP gateway. It operates as a repeater but also allows users to communicate with other networks via the gateway. The gateway connects to the repeater via the accessory connector.

Let's assume that in this repeater, TX Audio priority is set to 0 and Repeater Audio Priority is set to 3.

If a call comes in via the gateway, the repeater starts transmitting and uses the audio coming from the other side via RoIP. If any radio user tries to transmit, the repeater will not relay their voice - this is because the TX Audio path/input has the stage.

If a radio user presses PTT and a call comes in on the gateway at exactly the same time, the radio users audio will be transmitted. The repeater transmission will also follow the radio users transmission which means that the audio and PTT coming from the gateway will be lost.

Had TX Audio and Repeater Audio Priority been set to the same value, it would be the luck of the draw.

The probability of two sources transmitting at exactly the same time is pretty rare but there needs to be a means to decide which input has the stage in those cases.

To have a mix of external and repeated audio going out will require something external to the repeater. This custom-built-thing would need to sum the audio from the repeater's receiver as well as the audio coming from the external source. It would also need to OR the carrier detect and external PTT sources so that the repeater transmits when either input goes active.

An electronics person would be able to knock up a circuit and PCB design in a few hours. And, if you don't mind a single-sided PCB and the lack of solder mask, you could have a finished product within a day.