Select-5 in the DP and DM series

Select-5 is a type of squelch protocol used in analogue radio systems, in which transmissions consist of or include a burst of sequential audio tones. Receiving radio that are set to respond to the transmitted tone sequence will either open their squelch or carry out an action.

Select-5 (otherwise known as 5-Tone) is mainly in used outside the Americas and continues to be included with radio equipment sold in these regions.

The following radios support Select-5 signaling:
DP4400; DP4401; DP4400e; DP4401e; DP4401Ex
DP4600; DP4601; DP4600e; DP4601e
DP4800; DP4801; DP4800e; DP4801e; DP4801Ex
DP3441; DP3441e; DP3661e
DP2400**; DP2600**; DP2400e; DP2600e
SL1600*; SL2600*
DM4400; DM4400e;DM4401; DM4401e
DM4600; DM4600e;DM4601; DM4601e

These radios support the following tone formats:
- ZVEI 1 (sometimes known as DZVEI)
- ZVEI 2
- ZVEI 3 (sometimes known as PZVEI)
- CCIR with 100ms: 70ms and 20ms tone duration.

For systems that do not support any of the above formats, it is possible to define up to two custom User Defined signalling formats.

The burst described above consists of a Telegram. This Telegram will consist of between one and three Sequences. There is usually a short pause between each sequence. Each sequence will consist of up to 20 digits consisting of:

- Fixed Hexadecimal numbers: 0 to 9 and A to F
- Up to eight variable address digits entered in the CPS as A1 to A8 within brackets.
- Up to three status digits represented by entered in the CPS as S1 to A3 within brackets.
- And two special digits represented by T1 and T2. 

By default A and E are reserved for Group and Repeat and should not be used for individual radio numbers.

A group digits is the wildcard in a sequence. For example if a radio were to send 123AA, all radio which are configured to respond to 123xx will either open their squelch or carry out the configured action.

Select-5 cannot differentiate between two sucessive tones with the same frequency (digit) therefore the radio will automatically substitute the 2nd sucessive number with the repeat digit. So the sequence 12233 will actually be sent as 12E3E and 00000 will be sent as 0E0E0 -  no user intervention is required other than avoiding E as a digit in the entered sequence.

A radio will send the Telegram if:

- The user presses a button configured to send this Telegram.
- The radio receives a Selective Call; Stun; Un-stun or Silent Interrogate and is configured to send - an Auto Acknowledge.
- On power up or power down - if configured to do so.
- On pressing or releasing the PTT - if configured to do so.

In the below example, the radio has been provisioned with three sequences. The radios unique number in this case is 0001. The leading two digits signify what the sequence will be doing: 01 for PTT ID and 02 for selective call.

I have given names to these sequences to aid in configuring the radios. Sequence 1 (PTT-ID) is sent using Telegram 1. Sequence 2 and 3 (SelCall- and Caller ID) are sent in Telegram 2:

Telegram 1 is sent when the PTT is pressed:

Note that to see the above two fields, you need to add a 5-Tone Channel to the Zone. These fields are not visible in Conventional (MDC1200/QCII) Channels.

Call 1 will send Telegram 2:
And pressing button P1 will envoke Call 1:

On the receiving side, two decoder definitions would be needed: one for showing the PTT-ID of other radios and the other for handing the selective call.

One more thing: don't forget to "enable" the above decoder definitions in the 5-tone channel:

In a forthcoming post I'll be sharing how to improve the above configuration by adding features like auto-ack and auto-reset.

To get a general idea about Select-5, have a look at my old tutorial videos on YouTube covering the setup of the (no longer produced) GP/GM Professional Series.


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