Abstract: An envelope transport guide is disclosed that organizes opened and emptied envelopes from an envelope opening machine. The guide has an entry surface coplanar with the pathway of the moving envelopes, and adjacent the opening machine for accepting each envelope. The envelopes turn, under the force of gravity, around some guiding means and slide off the entry surface into an organized stack in an angled collection receptacle.

Abstract: A master station communicates with remote stations by respective transmit-receive pairs. Quadra-phase modulation is utilized, involving a carrier having two characteristic frequencies not present during bursts of a communicated signal, which bursts are known to last for a fixed duration. Signals on a receive pair are detected, and phase locked loops are tuned to the characteristic frequencies of the carrier and produce logical signals to indicate whether the characteristic frequencies are present. If not, a timer is energized to inhibit institution of a loopback condition for the duration of a data burst, after which the phase locked loops are permitted to enable the loopback.