[GreenKeys] RCA teleprinter ad on EBAY 381052171359 trans-atlantic

[Jim Haynes]

On Fri, 14 Nov 2014, Lester Veenstra wrote:

> When did the first "climbing head" TD's come out?
> These were used to "go back and repeat" in an ARQ system.
>
What I think of as a climbing head TD would not be useful for
go back and repeat, because it could only read in one direction.
I believe these were post-WW-II, used in the FRXD store-and-forward
machine for switching systems.

Western Union introduced a loopback tape reader in the 1950s for
Plan 55 switching system, but it was not for a go back and repeat
operation.  Rather it was to allow reading the message address
characters, setting up the connection, and then resending the address
characters to the destination.

Teletype had a bidirectional tape reader circa 1959 that was used in
the so-called Delta ASR set, the switching system for Delta Airlines.
But there the use was to store a multiple-address message and
go back and repeat it for each address it was to be sent to.