. The Bell System technical journal . sed of an alternate succession of speeches, defined and separatedby intervals, the lengths of which will be called response times. Anambiguity occurs when both parties talk simultaneously but, for thepurpose of this discussion, it will be sufficient to allow for this situationby admitting negative response times. Figure 1 represents a generalized four-wire circuit equipped with twoecho suppressors located at different distances from the ends of thecircuit. The transmission times of the different parts of the circuit are ^Characteristic Time Intervals in Te
. The Bell System technical journal . sed of an alternate succession of speeches, defined and separatedby intervals, the lengths of which will be called response times. Anambiguity occurs when both parties talk simultaneously but, for thepurpose of this discussion, it will be sufficient to allow for this situationby admitting negative response times. Figure 1 represents a generalized four-wire circuit equipped with twoecho suppressors located at different distances from the ends of thecircuit. The transmission times of the different parts of the circuit are ^Characteristic Time Intervals in Telephonic Conversation, A. C. Norwineand O. J. Murphy, this issue of the Bell System Technical Journal. THE OCCURRENCE AND EFFECT OF LOCKOUT 261 indicated on the figure with appropriate subscripts and the two direc-tions of transmission are differentiated by the primed and unprimednotation. The suppression points are indicated by arrows which repre-sent an opening of the transmission path when the relays, or other sup- fw+T+Te=T w —. — E Tyv+r + Te^T Fig. 1—Schematic of generalized four-wire circuit equipped with twoecho suppressors. pression devices are operated. The suppressing relays are specifiedby a notation which refers either to the particular relay or to its hang-over, or releasing time. According to the definition given above alockout exists during the time that both the relays he and hj areoperated.* With the exception of the beginning and end of the conversation theoccurrence of lockout can be described in terms of the resumption andresponse times following a pause by one talker, and the constants ofthe circuit. Referring to Fig. 1, and considering the sequence of eventsfollowing a pause by E, we shall see that two types of lockout can occur. The first type, which is the one usually met in practice, can occurwhen he < hw -\- r, and hw releases after he. A response by W and aresumption by E are necessary to produce a lockout. It will persist aslong as both E a
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