Re: RJE

On a DB25 connector, pin 15 provides receive clock and pin 24 provides
terminal clock. Crossing the two will provide the necessary clocking for a
null modem synchronous cable when both sides are providing clocking.

If only one side is providing clocking, then you hook the terminal clock
from the side providing clocking (pin 24) to pin 15 (receive clock) on both
sides, as well as pin 17 (transmit clock) on the side not providing
clocking.

Joe

On Wed, Apr 10, 2019 at 7:46 AM Ken Smyth [email protected]
[hercules-390] <[email protected]> wrote:

>
>
> Peter is correct, need a synchronous "null modem" to supply clock signal.
> Although sometimes the DTE equip has an option to provide clock, in that
> case the TX clock on one side is flipped over to the RX clock on the other
> along with the TX & RX signals. Control leads need to be hacked also
> depending on whether you are simulating a full or half duplex circuit.
>
> On April 10, 2019 at 7:57 AM "Peter Coghlan [email protected]
> [hercules-390]" <[email protected]> wrote:
>
>
>
> Joe Monk wrote:
> >
> > Dave,
> >
> > If you have a null modem cable, you can attach it directly to a serial
> port
> > on a 37X5 FEP...
> >
> > Joe
> >
>
> I'm a bit rusty on synchronous comms but I fear you may need a little more
> than a null modem cable. I think you may also need something to provide the
> clock signal which would normally be provided by one of the synchronous
> modems
> that are not present. Of course, if you had a pair of synchronous modems
> connected by a line simulator that would probably work.
>
> A leased line simulator might be as simple as one or two twisted pairs of
> wire.
> A dialup line simulator based on a single twisted pair and maybe a battery
> might be enough if the modems don't need to detect dialtone etc.
>
> Regards,
> Peter Coghlan.
>
> >
> > On Wed, Apr 10, 2019 at 5:52 AM Ken Smyth [email protected]
> > [hercules-390] <[email protected]> wrote:
> >
> > >
> > >
> > > That 3774 unit will have a synchronous RS232 type comm interface. It
> > > should be configurable for either SDLC or BSC, either way you will
> need a
> > > 37xx communications controller (aka FEP), ICA, or a 270x communications
> > > adapter on the mainframe side. As far as Hercules, I seem to remember
> there
> > > is a 270x BSC emulation using sockets, so it would be possible to
> build a
> > > 'black box' to accept socket connections on one side and drive an RS232
> > > sync interface on the other. Need to find a PCI or other synchronous
> RS232
> > > card which probably are not that common anymore.
> > >
> > > On April 8, 2019 at 9:58 PM "Dave McGuire [email protected]
> > > [hercules-390]" <[email protected]> wrote:
> > >
> > >
> > >
> > >
> > > So LSSM/MACT just took delivery of a 3774 RJE station, with
> > > peripherals, donated by IBM. It came with a punch, a reader, and a line
> > > printer. It all appears to be complete except for a missing space
> > > bar...that's kinda heartbreaking. On the off chance that anyone here
> > > might know of some old parts closet where one might be found, please
> > > drop me a note.
> > >
> > > I've only just started to look around for information about this
> > > system. Does anyone here know anything about it?
> > >
> > > Ideally, I'd like to get it up and running to talk to some of the
> > > mainframes at the museum, but it would be very interesting to get it
> > > talking to Hercules as well. Thoughts?
> > >
> > > Thanks,
> > > -Dave
> > >
> > > --
> > > Dave McGuire, AK4HZ
> > > New Kensington, PA
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> >
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