Black Box MD3318 Modem User Manual


 
10
SHORT HAUL MODEM (SHM-FSK)
2.3 Operating Mode
The SHM-FSKs can be operated in either point-to-point or multipoint polling
mode.
For multi-drop data communications, the SHM-FSK can be operated with
one Master and typically up to eight Remote units. The transmitter in each
Remote unit is controlled by the intelligent device it is connected to. The
Master unit’s transmitter remains on all the time. The green two-position
pluggable terminal block at the receptacle marked “LINE” on the back of the
SHM-FSK unit is used with any two-wire cable (does not need to be twisted).
Since the FSK signal is AC, there is no polarity required on any of the data-
line connections.
2.4 Diagrams
Figure 2-1 shows the location of the LEDs on the front of the SHM-FSK.
CD RxD TxD LPBK PWR
Figure 2-1. Location of LEDs on the SHM-FSK.