Transponder Goes Up To 8

I find myself holding a 747 transponder control head that I bought on
eBay as a toy for the kids. But, with echos of Spinal Tap's guitarist
in my head, I notice that the selector knobs allow the digits 0 thru 8
to be selected. What gives?

Actually 0-7. Three bit octal. All transponder codes are four digits - each
digit is 0-7. Technology comes VERY slowly to aviation.


"Mike Granby" wrote in message
...

I find myself holding a 747 transponder control head that I bought on
eBay as a toy for the kids. But, with echos of Spinal Tap's guitarist
in my head, I notice that the selector knobs allow the digits 0 thru 8
to be selected. What gives?

pgbnh wrote:
Actually 0-7. Three bit octal. All transponder codes are four digits - each
digit is 0-7. Technology comes VERY slowly to aviation.


"Mike Granby" wrote in message
...
I find myself holding a 747 transponder control head that I bought on
eBay as a toy for the kids. But, with echos of Spinal Tap's guitarist
in my head, I notice that the selector knobs allow the digits 0 thru 8
to be selected. What gives?




I think that is Mike's point. He is holding one that goes 0-8.

Mike Granby wrote:
I find myself holding a 747 transponder control head that I bought on
eBay as a toy for the kids. But, with echos of Spinal Tap's guitarist
in my head, I notice that the selector knobs allow the digits 0 thru 8
to be selected. What gives?

Just curious - but does it look like either of these:
http://www.angelfire.com/il2/aphs/txp2.jpg
http://www.angelfire.com/il2/aphs/txp.jpg

Or is it a LED display?

On Dec 19, 6:06 pm, Jim Logajan wrote:

Just curious - but does it look like either of these:

http://www.angelfire.com/il2/aphs/txp2.jpg
http://www.angelfire.com/il2/aphs/txp.jpg

Similar to botrh, but identical to neither.

Here's the eBay link...

http://cgi.ebay.com/ebaymotors/ws/eB...m=230199151135

On Thu, 20 Dec 2007 06:34:11 -0800 (PST), Mike Granby
wrote in
:


Here's the eBay link...

http://cgi.ebay.com/ebaymotors/ws/eB...m=230199151135

That indicates that it's a: GABLES ENGINEERING, MOD. NO. G-1884C

There's a link to Gables products he
http://www.gableseng.com/rotary.asp but I don't see the G-1884C among
them. However, you can request a password he
http://www.gableseng.com/dds.asp to view the on-line documentation for
their products. Surely the eight digits would be explained there.

Also interesting is the 1884C's Volume control!

On Dec 20, 11:26 am, Larry Dighera wrote:

Also interesting is the 1884C's Volume control!

It's also a control head for a MB receiver.

That control is labelled MARKER, and also selects senstivity.

Larry Dighera wrote:
On Thu, 20 Dec 2007 06:34:11 -0800 (PST), Mike Granby
wrote in
:

Here's the eBay link...

http://cgi.ebay.com/ebaymotors/ws/eB...m=230199151135

That indicates that it's a: GABLES ENGINEERING, MOD. NO. G-1884C

There's a link to Gables products he
http://www.gableseng.com/rotary.asp but I don't see the G-1884C among
them. However, you can request a password he
http://www.gableseng.com/dds.asp to view the on-line documentation for
their products. Surely the eight digits would be explained there.

Also interesting is the 1884C's Volume control!


From the same seller.

http://cgi.ebay.com/P-3-Aircraft-Pil...QQcmdZViewItem

That would be fun just to stick into the empty space on the panel of a
homebuilt.

In article ,
says...


Larry Dighera wrote:
On Thu, 20 Dec 2007 06:34:11 -0800 (PST), Mike Granby
wrote in
:

Here's the eBay link...

http://cgi.ebay.com/ebaymotors/ws/eB...m=230199151135

That indicates that it's a: GABLES ENGINEERING, MOD. NO. G-1884C

There's a link to Gables products he
http://www.gableseng.com/rotary.asp but I don't see the G-1884C among
them. However, you can request a password he
http://www.gableseng.com/dds.asp to view the on-line documentation for
their products. Surely the eight digits would be explained there.

Also interesting is the 1884C's Volume control!


From the same seller.

http://cgi.ebay.com/P-3-Aircraft-Pil...l-Panel_W0QQit
emZ230203538491QQihZ013QQcategoryZ36074QQcmdZViewI tem

That would be fun just to stick into the empty space on the panel of a
homebuilt.


What's funny about it?
It's a standard-issue armament panel from a Vietnam era Beech Baron.
You'll find it right next to the ejection seat actuator.

Here's the answer from a very kind soul at Gables...

The G1884 series started in 1965. I started in this business in
1967. I don't know the whole story but back then ACT control
panels allowed all 8's to be selected. Something to do with a
"remote keyer" function. Apparently this function was never
adopted and later revisions to product and newer part numbers
only allowed 0 thru 7 selections on each digit.

So there you have it! 8888 presumably put the code under remote
control from some other piece of equipment.