An improved conference circuit
M.V. Pitke, T. Chandrasekaran · Proceedings of the IEEE · 1983
A conferencing scheme based on signal addition has been presented. Use of alternating inverting amplifier stages at the summing circuits considerably cancels out the effect of feedback voltages due to poor return loss of the hybrids. In the worst case, the net feedback voltage due to return loss at any subscriber line circuit is no more than twice than that encountered in one-to-one connection.