[ARC5] Unknown control box

[Sheldon Daitch]

Perhaps it is a prototype unit - I have no idea.  I understand the ergonomics concern, but considering what appears to be the age of the unit, maybe that wasn't a driving force at the time.



Some semieducated guesses here.

In many aircraft NAV/COM systems, the DME receiver is slaved off the NAV radio frequency selection and there would be a need to torn the DME function on or off.

Slaving the DME transmitter/receiver off the NAV radio controller is both a convenience factor and a panel space concern.  One less radio control to have to deal with while in flight.
Most DME system frequencies are paired to VHF nav frequencies and if a DME is located at a VOR facility, either VORTAC or VOR-DME, the DME system is set up for that VOR frequency.  I seem to recall that some of the TACAN DME frequencies can be used for DME but not all TACANs match the VHF/DME frequency pairing.

Yes, High/Low receiver sensitivity is used, as discussed below, with marker beacons, but again, guessing here, I'd submit the High/low in this case is the audio level from the DME receive side to the audio panel of the aircraft so the pilot can monitor and verify the call sign of the DME station.

73
Sheldon






-----Original Message-----
From: ARC5 [mailto:arc5-bounces at mailman.qth.net] On Behalf Of D. Platt
Sent: Tuesday, July 15, 2014 7:57 PM
To: arc5 at mailman.qth.net
Subject: Re: [ARC5] Unknown control box

In my humble opinion, its a control box, and probably a prototype at that.  The reason I say proto is that the function switch is not human engineered properly.  The knobs are way too close together and any ergo-engineer would handily reject the design.  The fact that DME is even mentioned is arguably for control purposes, only.  And, what does "DME off" mean?  Is it the R/T unit or the audio ident? The low/stby and hi refers to what?  Selectable low/high us usually relegated to the 75Mhz marker beacon receiver.  Now, it may well be that the concentric freq knobs are the wrong ones.  If smaller ones were used, maybe the selector switch would be OK?  Again, it screams out to be a proto box as it does not comply with any standard ARINC label or layout.

Jeep - K3HVG
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