Multiplex communications – Wide area network – Packet switching
Patent
1984-12-10
1986-11-11
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
370105, H04J 306
Patent
active
046226664
ABSTRACT:
A framing circuit is disclosed for detecting framing bits in a t.d.m. bit stream having an extended DS1 framing format. The circuit comprises a RAM for storing in respect of each of the 772 time channels the five most recent information bits of the time channel and three other, candidate, bits which represent the likelihood that the particular time channel carries the framing bit pattern. The current and five stored information bits of each time channel are checked to detect the six-bit framing bit pattern. The candidate bits have their value increased or decreased, within predetermined limits, in dependence upon whether or not a phase of the framing bit pattern is detected, and the updated information and candidate bits are stored in the RAM. The modification of the candidate bits in this manner is effected in only every third 772-bit frame. A framing signal is produced in dependence upon the candidate bits.
REFERENCES:
patent: 3903371 (1975-09-01), Colton et al.
patent: 3928726 (1975-12-01), Colton et al.
patent: 4298987 (1981-11-01), Stattel et al.
patent: 4301534 (1981-11-01), Genter
AT&T Technical Advisory No. 70, Issue No. 2, Sep. 29, 1981.
Graves Alan F.
Littlewood Paul A.
Weiss Johannes S.
Haley R. John
Northern Telecom Limited
Olms Douglas W.
Rokoff Kenneth I.
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