Help identifying wireless doorbell signal

Get help identifying an unknown signal.
kwl3
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Joined: Thu Feb 22, 2018 8:54 am
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Re: Help identifying wireless doorbell signal

Post by kwl3 » Thu Aug 30, 2018 6:01 pm

After looking at the codes sent by the three of these doorbells I have physical access to, and recreating variations of their signals using a YARD Stick One (YS1), here's my stab at what these 48 bits of data might indicate:

Code: Select all

# Honeywell SERIAL ID BITS
# 0000 0000 0000 0000 1111 1111 1111 1111 2222 2222 2222 2222
# 0123 4567 89ab cdef 0123 4567 89ab cdef 0123 4567 89ab cdef
# .... .... .... .... .... .... .... .... .... .... .... ...X CHKSUM (LSB of sum of set bits in previous 23 bits)
# .... .... .... .... .... .... .... .... .... .... .... ..X. LOWBAT (1 if battery is low)
# .... .... .... .... .... .... .... .... .... .... .... .X.. IGNORED? (My receivers don't seem to care either way)
# .... .... .... .... .... .... .... .... .... .... .... X... RELAY (1 if signal is a retransmission of a received transmission, only some models)
# .... .... .... .... .... .... .... .... .... .... ...X .... SECRET KNOCK (if doorbell is pressed 3x rapidly)
# .... .... .... .... .... .... .... .... .... ..XX .... .... ALERT (00 = normal, 01 or 10 = right-left light pattern, 11 = full volume alarm)
# XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX XX.. XXX. .... KEY (any change and receiver doesn't recognize signal)
# XXXX XXXX XXXX XXXX XXXX .... .... .... .... .... .... .... KEY ID (different for each transmitter I've tested)
# .... .... .... .... .... 0000 00.0 0000 0000 00.. 000. .... KEY UNKNOWN 0 (always 0 in devices I've tested)
# .... .... .... .... .... .... ..1. .... .... .... .... .... KEY UNKNOWN 1 (always 1 in devices I've tested)
Some observations:
  • Some receiver models (like the Honeywell RDWL917AX2000/E Series 9) will immediately retransmit any valid received signal that does not already have the RELAY bit set. This seems like a useful feature to help extend the range of a signal to a more distant receiver. However the retransmission will have the RELAY bit set, so there could only be one retransmission.
  • The ALERT bits seem to indicate the receiver should take some special action. One some receivers, that action might be to blink its lights in a different pattern, or to play a siren at full volume.
The code that tos7 found on his device (FF 73 70 20 00 01) and posted above also seems to fit in with this scheme.

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