Standard User Interface Drawings

This is a work in progress and is presented to encourage discussion and refinement in order to document a standard solution.

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This page is a collection of drawings and wiring diagrams for the Standard User Interface

Prototype Drawings

The Standard User Interface defines the connections and wiring, but does not specify the cabinet in which to build the interface. The purpose of the interface is to establish a standard capability and the wiring to support that capability.

Front View

The front view shows the jacks, switches, volume controls and indicator lights that would be included in the user interface.

User Interface Diagram
LED Indicators
Power - Indicates that the User Interface has 12 VDC power from the standard interface connector.
PTT Active - Indicates when PTT is active and which operator has activated it.
Headphone jacks are 3.5mm (1/8") stereo phone plugs. This is will accept any of the headsets made for stereos today as well as many of the commercial radio headsets.
Microphone / Headset
The Microphone / Headset jacks are 2.5mm (3/32") stereo phone plugs. This is only an idea at this time, but this is the same jack used in most cordless phones and cell phones. There are many commercial headsets available, that are wired with the plug for this jack. The idea is to use this for any microphone inputs, by providing microphone bias voltage at the jack, while also providing a mono headset connection.
The PTT jack is a 2.5mm (3/32) mono phone plug. This can be used to plug in a hand switch or for headsets that have a built in PTT switch. There is a second PTT jack on the back of the user interface to plug in a foot switch, so the users can have the option to make it easier during extended periods of operation.
HP Volume
Each user has their own headphone volume control
HP L and R Switch
Each user has a switch that will disable one side of there headset, to make it easier to converse with the person next to them. The left users switch turns off the right side of their headset, while the right user's switch turns off the left side of their headset. The other position for the switch will turn off one side of the headset and connect it to the auxiliary. input from the back of the unit. This allows a second radio or scanner to be connected to the auxiliary input, so the operators can listen to 2 radios at once.
Auxiliary Volume
Each user can adjust the auxiliary input volume for their headset.
Speaker Volume
The speaker volume controls the output of the speaker jack on the back of the user interface box. If there is a message on the radio that someone needs to hear, the operators can turn up the speaker. The speaker could also be on an extension, so the group being supported can listen to the radio.

Back View

The back of the user interface box has the connections that are not required on the front of the box.

User Interface Back View
The DA15 IN connector plugs into the Standard Radio Interface. The User Interface could be beside the radio, or extended up to several hundred feet using an extension cable. The IN connector provides all the radio interface signals as well as 12VDC.
The DA15 OUT connector is wired to the IN connector. The OUT connector allows a second user interface to be extended for the same radio. The extra user interface may be at the other end of the same table, or could be on the other side of the room.
The PTT jack is a 2.5mm (3/32) mono phone plug. This can be used to plug in a foot switch. There is a second PTT jack on the back of the user interface to plug in a hand switch or for headsets that have a built in PTT switch, so the users can have the option to make it easier during extended periods of operation.
The Speaker jack is a 3.5mm (1/8") mono phone plug. This allows an external speaker to be plugged in, without the users having to unplug headsets. The speaker could be located beside the users for occasional listening or could be extended along the table or to another part of the room to allow other participants to listen.
auxiliary Input
The auxiliary Input jack is a 3.5mm (1/8") mono phone plug (another option is RCA). This allows a second receiver to be connected to one side of the users headset. The extra radio could be an FRS radio, scanner or another amateur radio. If it is an amateur radio with the standard interface, then an adapter is required.

Internal View

The internal view shows a sort of top side, looking into the box view.

User Interface Internal View

The User Interface will require a few innovative wiring techniques. Many of these ideas are from the CAIRO documentation. The UK group did a lot of thinking when they developed their system.

There is a resistor in line with the headphone jack to limit the signal level. The jack on the back of the radio is for an external speaker and headphones connected directly to that can provide signal levels that hurt hearing. The resistor is a safety feature to limit the signal level.
Headset Volume
There is a resistor in line with the headset volume, so the user cannot turn the volume all the way down. Even with the volume control turned all the way down, there will still be some signal in the headset.
PTT switching will be required to activate the correct microphone and PTT LED indicator. This will ensure that the other operators microphone is only on if that operator pushes the PTT. This avoids a problem of having both microphones on, when one operator is activating PTT, and the other operator is having a conversation with someone.
The speaker jack is a switching type, so there is an 8 ohm resistor across the terminals when no speaker is connected. Plugging in a speaker, will bypass the resistor. This is an idea that has not been tested, but the concept is that this may limit signal level changes for other users when a speaker is added or removed from the system.
Microphone Bias
Most microphones require a low level microphone bias voltage. The voltage will be supplied using the auxiliary 12VDC from the Standard Radio Interface, with a voltage regulator.

Extension Cables

One of the big advantages of implementing the Standard Radio Interface and the Standard User Interface, is the ability to use an extension cable to locate the user up to several hundred feet from the radio. The extension cable will be smaller and more flexible than coax and the several hundred feet does not impact the final output from the radio.

Exceptionally long cables require individual shielding of signal cables. Belden makes a 5 wire cable with 3 wires individually shielded. For the end user application, 5 wires is sufficient. Here is a sample extension cable.

Long Extension

There are some issues with extension cables, regarding how the shielding is handled. Option 1 uses pin 1 to connect the shield between each section, making an end to end cable shielding. Option 2 attaches the shield to signal ground, freeing up pin 1 for other purposes.

Cable Shielding Options