Here’s a photo showing the 6-TD dual-bank setup.
However the second bank may have just been used for a pre-punched message number tape. Every outgoing message had to have a header with channel ID and sequential message number.
The military AN/TGC-1 relay unit had three TDs, one for the header/number tape and the other two for messages in ping-pong fashion.
Later Navy message transmitters used an electromechanical (or electronic) header/number unit plus ping-pong TDs. These were arranged in groups of three. Here’s one I have restored with videos showing operation.
As you can tell I am fascinated by torn tape relay operation.
More info/photos at
On Mon, 23 Sep 2024, Nick England wrote:
> Used in a tape relay center to transmit outgoing messages with each TD
> connected to a line to a different destination.
>
It was also fairly common to have two TD heads feeding the same outgoing
trunk, arranged so that only one at a time could transmit. This allowed
the sending operators to have at least two outgoing messages in queue
for transmission without any need to attend to the machines once the
tapes were loaded on.
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"Ya can argue all ya wanna, but it's dif'rent than it was."
"No it ain't! No it ain't! But ya gotta know the territory."
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