Our ISP provided a Thompson dwg855 at installation of our service. We need greater coverage. Is is possible to use the output port on the modem to connect to a wireless router or other wired device? Thanks in advance for your assistance.
Yes, you can attach a wireless router configured as an access point. Something like a Linksys WRT54GL would work well.
Run CAT 5e cable from an LAN port on the dwg855 to an LAN (not WAN) port on the wireless router. In new wireless router: use a different radio channel than the dwg855, same SSID (network name), same security passphrase, and turn off the DHCP service. The new router needs to have an IP address that is in your network but outside of the IP address range that your dwg855 DHCP service assigns.
So, for example, if your dwg855 has a gateway address of 192.168.0.1, assign the new router (configured as an AP) an address of 192.168.0.2 and allow the dwg855 assign addresses 192.168.0.3 to .254.