joining 2 lines into single one

Shell Programming and Scripting
1

i have a script that joins 2 lines of a file into one line and again next 2 line into one line.

if number of line is 4 then after joining it should be 2 lines in a file

my file a1.txt has some of the below lines

1-GH32X, CC, AMR,
Number of Intervals Not Inserted: 1 / 95
1-150KP1, CC, AMR,
Number of Intervals Not Inserted: 1 / 96
1-VWEMR, CC, AMR,
Number of Intervals Not Inserted: 1 / 98
1-15HM1A, CC, AMR,
Number of Intervals Not Inserted: 1 / 99
1-153PIV, CC, AMR,
Number of Intervals Not Inserted: 3 / 99
------------------------------------------------------------------------
desired o/p should be :

1-GH32X, CC, AMR,Number of Intervals Not Inserted: 1 / 95
1-150KP1, CC, AMR,Number of Intervals Not Inserted: 1 / 96
1-VWEMR, CC, AMR,Number of Intervals Not Inserted: 1 / 98
1-15HM1A, CC, AMR,Number of Intervals Not Inserted: 1 / 99
1-153PIV, CC, AMR,Number of Intervals Not Inserted: 3 / 99

i m using the below command but it's not joining properly

paste -s -d" \n" a1.txt >> a2.txt

-----------------------------------------------------------

plz help me in this?

2 
awk '/^[0-9]/{printf "%s",$0;next}1' file >> new.file
3 
> cat file120
1-GH32X, CC, AMR,
Number of Intervals Not Inserted: 1 / 95
1-150KP1, CC, AMR,
Number of Intervals Not Inserted: 1 / 96
1-VWEMR, CC, AMR,
Number of Intervals Not Inserted: 1 / 98
1-15HM1A, CC, AMR,
Number of Intervals Not Inserted: 1 / 99
1-153PIV, CC, AMR,
Number of Intervals Not Inserted: 3 / 99

> sed "s/[0-9]$/&~/" file120 | tr -d "\n" | tr "~" "\n"
1-GH32X, CC, AMR,Number of Intervals Not Inserted: 1 / 95
1-150KP1, CC, AMR,Number of Intervals Not Inserted: 1 / 96
1-VWEMR, CC, AMR,Number of Intervals Not Inserted: 1 / 98
1-15HM1A, CC, AMR,Number of Intervals Not Inserted: 1 / 99
1-153PIV, CC, AMR,Number of Intervals Not Inserted: 3 / 99
>
4

Or:

awk 'ORS=NR%2?FS:RS' infile

sed 'N;s \n  ' infile