On the telnet prompt do: 
  {FS20_Parse(undef, "<code>");}
e.g.
  {FS20_Parse(undef, "81xx04xx0101a0011234030011")}

where <code> is one of:

81xx04xx0101a0011234030011	FS20 dev: 1234  button: 03 on  (11)
81xx04xx0101a0011234030000	FS20 dev: 1234  button: 03 off (00)

810d04xx4027a001de53187654321f	KS300: Raincounter hex:123 (ca 75l/m2),
				Wind 45.6 km/h Humidity: 78%, Temp: 13.5
				Unknown fields: d,e,f
{FhzDecode("810d04xx4027a001de53187654321f")}

810e04d70213a001b16d000003000000  RM100-2 smoke on
810e04d70213a001b16d000000000000  RM100-2 smoke off

81xx04xx0101a0011234030011	FS20 dev: 1234  button: 03 on  (11)

To send it:
set FHZ raw 04 0101a0011234030011