Has your string TelephoneNo been converted to ASCII first?

Except for the first example being terminated with CR, ASCII conversion
handled in-line, and the number of digits dialed, it looks like both should
work the same.

Does something like his work?
Code:
STRING VAR BYTE[6]
X VAR BYTE

MAIN:
    FOR X = 0 TO 5
    STRING[X] = X + "0" ' convert digits to ASCII
    NEXT X    
    HSEROUT [34,STR STRING\6,34]

DONE:
    GOTO DONE