Registration¶

After the data link comes up, and again after every link re-establishment, the phone identifies itself. Until the PBX replies, the phone repeats the message periodically.

sequenceDiagram
  participant P as Phone
  participant N as PBX
  P->>N: STATUS ENQUIRY (0x75) with identification
  N->>P: RELEASE COMPLETE (0x5A) with PBX id, date/time
  P->>N: STATUS (0x7D), cause 95, call state 0, empty cs7 element 02

Phone to PBX¶

Message type 75 (the standard STATUS ENQUIRY value, used here for identification), call reference 01, flag 0. ✅ Tested:

08 01 01 75
97
01 08 50 53 31 33 30 33 35 37                       element 01: "PS130357"
0f 37 ff ff 00 00                                     further elements, not decoded
06 "V5.250"                                           length 6, firmware version string
11 "12/08/15 15:04:01"                                 length 17, build date string
01 ff
12 ff ff ff ff ff ff ff ff ff ff ff

• The first message is the long form above. Retries carry only 97 01 08 "PS130357".
• PS130357 identifies the terminal class. The PBX distinguishes classes by this string; other strings seen in the PBX tables are US050561, UR230560, DTDECT01 and DTAG0104 (other terminal types). 📖 Read from the PBX's tables, 🔶 meaning inferred.
• The octets 06 and 11 in front of the version and date strings are their lengths (6 and 17 characters). The element ids that go with them, and the other octets (0f 37 ff ff 00 00, 01 ff, 12 ff ...), are ❓ Unknown.

PBX to phone¶

A RELEASE COMPLETE using the phone's call reference with the flag set:

08 01 81 5a
08 02 85 d1                       cause 81, location 5 (optional in effect)
29 05 yy mm dd hh mi              date and time, binary (optional)
97
01 08 44 57 31 33 30 39 35 38     element 01: "DW130958", the PBX identification
26 02 82 80                       constant (optional in effect)

✅ Tested:

• the phone stops repeating, sets its clock from the date/time element and adds a Tel. drctry entry to its idle menu;
• the reply must be type 5a, must carry the call reference flag, and must contain codeset 7 element 01;
• a header-only reply, a reply with the flag clear, or another message type (7d was tried) is ignored and the phone keeps repeating;
• the cause location (85 or 81) and element 26 make no visible difference; the date/time element is optional.

The STATUS that follows¶

A short time after any accepted reply the phone sends

08 01 01 7d | 08 02 80 df | 14 01 00 | 97 02 00

a STATUS for call reference 1 with cause 95, call state 0 (null) and an empty codeset 7 element 02. It is sent regardless of what the reply contained, and the tests needed no answer to it. Meaning of the empty element: ❓ Unknown (it is the system-phone data container, see Codeset 7).

Re-registration¶

If the PBX stops answering polls the phone re-establishes the link and registers again, with the next call reference (02, then 03, ...). The PBX must reply to each.