Cser Laszlo wrote:

> This one at midcom only works at 2400bps full duplex and in some cases
> 14.4kpbs half duplex as the text states. What is preventing the
> circuit from performing at higher speed in full duplex mode?

  Hey, read the article!  It tells you that the transformer performance
is limited by (its small size and) the fact that in this circuit the DC
current is flowing through the transformer.

  The load on the hybrid may also be less than optimum, and there is
possibly a tradeoff in the protection devices.

> Is it possible with the above circuit if I use a different
> transformer? The midcom transformer has 3.76dB max insertion loss at
> 1kHz. It has DC resistance of 152ohm each coil.  The different
> transformer I would use would be a Bourns SM-LP-5001 which has 2dB
> insertion loss and 115 Ohm resistance.

  Maybe, maybe not.  It has a lot to do with distortion.  Insertion
losses are trivial - signals can be amplified.

> The circuit uses a solid state relay in the Line part. It is a NEC
> PS7342C-1A or Solid State Optronics AD6C111-N model. Do you know
> additional firms who manufacture similar telephone Solid State Relays?

  You can always consider a *real* relay.  Consumes more current, but
less distortion (gets back to the ability to run 33k6 baud too!).
--
  Cheers,
        Paul B.