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Software Usage and Examples
because of the parallel circuit, and the pulses will not be dialed. Consequently, a phone cannot be used as
J
a line monitor while pulse dialing.
The best solution is to identify when it is safe to pick up the phone and listen to it. This point in time can
be predicted by calculating how long it will take to pulse dial the number. From the worst-case pulse
dialing times just listed, it is easy to develop an algorithm to compute the time
T
to pulse-dial the phone
number. Once the modem begins to dial and echoes the dialed digits of the phone number,
T
seconds must
elapse before the phone can be picked up by the user.
The program below illustrates this timing technique.
D$
represents the dial string for the phone number
itself-no access codes. The second echoing of the phone number is used as the starting point for the
timing because the first echoing is spurious-it occurs as the modem receives the 0 (DIAL) command, not
when dialing actually begins. The first echoing of the dial string is read at line 100. The second echoing
occurs as the modem actually dials the number, and is detected at line 160.
The computation appears on lines 120-1 SO, and does not take into account W, P, *, or
,I,
none of which
would normally appear in a pulse-dialed phone number with no access codes. As the program converts
each character of the dial string into a number (line 140), illegal characters are trapped out (lines 120 and
150). Then the program accumulates the time to pulse each digit plus the interdigit delay (line 140). The
computation provides an extra margin of safety because of the time needed to compute the total dialing
time.
1 00 F;$: = "
~.~
D
"t:
D $
:~.:
C H F. : $ ( 1 ::: )
I~
t'W D 0 U T F $
I~
CO::; U E: 1 000
110 DI::;P "Do not. pick up phone!"
120 T=0
~
ON EF.:ROF.: COTO 150
130 FOF.: 1=1 TO LEN(D$)
140
V=VAL(UPF.:C$(O$[I~IJ»
@
T=T+(V+l0*(NOT V»/10+.8
150 NEXT I
@
OFF EF.:F.:OF.:
160 F;$:=D$
~
CO SUB 1000
~
T=T+TIME
170 IF TH1E<T
THEt·~
170 EL::;E DI:;:;P
"m:::
t.o pick up phone"
180 ! PrograM cont.inues
U300
::;$=""
1010 S$=S$tMODIN$
~
IF
POS(S$~F$)
THEN RETURN ELSE 1010
If access codes separated by waits appeared at the beginning of the dial string, the waits between the
access codes will halt echoing for the duration of the waits (refer to the 0 command). In that situation,
you should split the access codes off from the dial string, and use only the echoing of the phone number
itself as the starting point for timing.
Manual Dialing
Your application may allow the user to dial a phone number manually, The general procedure is:
1)
Ask if the user wants to dial the number manually.
2) If yes, the program must put the modem on-hook with the
H (HANGUP)
command in case the
phone being used to dial generates pUlses. Then the program should put up a message telling the
user to dial the number, and to press a key on the HP-75 after dialing. Then the program must
wait for the key to be pressed.
39
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