Ruby driver for an 8 Channel Relay Module USB type USB-RLY08 by Devantech. The driver needs the serialport gem installed. You will probably need to change the port name to the correct name.

relay_driver.rb

require 'rubygems'
require 'serialport'

class RelayDriver

  def initialize
    #params for serial port
    port_str = "/dev/tty.usbmodem00024841"  #may be different for you
    baud_rate = 19200
    data_bits = 8
    parity = SerialPort::NONE
    @serial_port = SerialPort.new(port_str, baud_rate,8,1,parity)
    @serial_port.read_timeout = 100
  end

  #relay number 1->8
  def close_relay(relay_number)
    command = 110 + relay_number
    @serial_port.putc(command)
  end

  #relay number 1->8
  def open_relay(relay_number)
    command = 100 + relay_number
    @serial_port.putc(command)
  end

  #closes all relais
  def close_all_relais
    close_relay 0
  end

  def get_relay_states
    command = 91
    @serial_port.putc(command)
    state = @serial_port.getbyte
    if state.nil?
    	puts "Error reading state: timeout"
    else
      state_array=Array.new
      (0..7).each do |i|
        state_array <<  (0 != ((1<<i) & state))
      end
      state_array
    end
    
  end

  def set_relay_states(state)
    command = 92
    @serial_port.putc(command)
    @serial_port.putc(state)
  end

  #opens all relais
  def open_all_relais
    open_relay 0
  end

  def close
    @serial_port.close
  end
end

dr = RelayDriver.new

dr.open_all_relais
dr.get_relay_states
sleep 0.1

dr.close_all_relais
dr.get_relay_states
sleep 0.1

(1..8).each do |i|
  dr.open_relay i
  dr.get_relay_states

  sleep 0.1
  dr.close_relay i
end

dr.open_relay 1
dr.open_relay 4
puts dr.get_relay_states.join(",") 
sleep 0.1

dr.close_all_relais
puts dr.get_relay_states.join(",") 
sleep 0.1

dr.open_relay 1
dr.open_relay 4
puts dr.get_relay_states.join(",") 
sleep 0.1

dr.open_relay 1
dr.open_relay 4
puts dr.get_relay_states.join(",") 
sleep 0.1

dr.close_all_relais
puts dr.get_relay_states.join(",") 
sleep 0.1

dr.close