sexpots: Entire modem init string not being sent

# cat < /dev/ttyACM0 &
[1] 5532
root@wibble:~# systemctl start sexpots
AT&F1s0=0m0l1s48=root@wibble:~#

As you can see, only part of the init string is sent.

Init = AT&F1s0=0m0l1s48=7s36=5&W