man/man4/dp.4

.pa 1
.he 'DP (IV)'3/15/72'DP (IV)'
.ti 0
NAME            dp -- dp-11 201 data-phone interface
.sp
.ti 0
DESCRIPTION     dp?\b\b\b___
is a 201 data-phone interface file.
read\b\b\b\b____ and write\b\b\b\b\b_____ calls to dp?\b\b\b___
are limited to a maximum of 400 bytes.
Each write call is sent as a single record.
Seven bits from each byte
are written along with an eighth odd parity
bit.
The sync must be user supplied.
Each read call returns characters received from a
single record.
Seven bits are returned unaltered; the eighth bit
is set if the byte was not received in odd parity.
A 20 second time out is set and a zero byte
record is returned if nothing is received in that time.
.sp
.ti 0
FILES           /dev/dp0        201 dataphone used to call GCOS
.sp
.ti 0
SEE ALSO        dn(IV), gerts(III)
.sp
.ti 0
BUGS            The dp\b\b__ file is
GCOS oriented.
It should be more flexible.