PLANET VIP-1680 - Manual (Page 12)

(CO line), and the FXS interface is designed for connecting to analog telephone sets or fax machines. If
the telephone cable connects to VIP-16/2480 series, the FXS interfaces are odd ports i.e. 1, 3, 5, 7, 9,
11, 13, 15, 17, 19, 21, 23, and the FXO interfaces are even ports, i.e. 2, 4, 6, 8, 10, 12, 14, 16, 18, 20,
22, 24.
12
Incorrectly connecting telephony devices to the RJ11 port
on the Telephony Interface can cause permanent damage to
the VoIP Gateway