Local Area Signaling Services
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Local Area Signaling Services (LASS) codes are numbers entered on a telephone touch-pad to access special calling features of the telephone system.
The most well-known LASS codes are *67 to toggle Caller-ID blocking and *69, for Call Return. LASS codes appear to be standard, but may be changed locally.
Local Area Signalling Services (LASS) and Custom Calling Feature Control Codes:
| Service | Tone | Pulse/rotary | Notes |
|---|---|---|---|
| Cancel forwarding | 30 | n/a | [C1] |
| Automatic Forwarding | 31 | n/a | [C1] |
| Notify | 32 | n/a | [C1] [2] |
| Intercom Ring 1 (..) | 51 | 1151 | [3] |
| Intercom Ring 2 (.._) | 52 | 1152 | [3] |
| Intercom Ring 3 (._.) | 53 | 1153 | [3] |
| Extension Hold | 54 | 1154 | [3] |
| Customer Originated Trace | 57 | 1157 | |
| Selective Call Rejection | 60 | 1160 | (or Call Screen) |
| Selective Distinct Alert | 61 | 1161 | |
| Selective Call Acceptance | 62 | 1162 | |
| Selective Call Forwarding | 63 | 1163 | |
| ICLID Activation | 65 | 1165 | |
| Call Return (outgoing) | 66 | 1166 | |
| Number Display Blocking | 67 | 1167 | [4] |
| Computer Access Restriction | 68 | 1168 | |
| Call Return (incoming) | 69 | 1169 | |
| Call Waiting disable | 70 | 1170 | [4] |
| No Answer Call Transfer | 71 | 1171 | |
| Usage Sensitive 3 way call | 71 | 1171 | |
| Call Forwarding: start | 72 or 72# | 1172 | |
| Call Forwarding: cancel | 73 or 73# | 1173 | |
| Speed Calling (8 numbers) | 74 or 74# | 1174 | |
| Speed Calling (30 numbers) | 75 or 75# | 1175 | |
| Anonymous Call Rejection | 77 | 1177 | [5] [M: *58] |
| Call Screen Disable | 80 | 1180 | (or Call Screen) [M: *50] |
| Selective Distinct Disable | 81 | 1181 | [M: *51] |
| Number Display Unblocking | 82 | 1182 | [4] [7] |
| Select. Forwarding Disable | 83 | 1183 | [M: *53] |
| ICLID Disable | 85 | 1185 | |
| Call Return (cancel out) | 86 | 1186 | [6] [M: *56] |
| Anon. Call Reject (cancel) | 87 | 1187 | [5] [M: *68] |
| Call Return (cancel in) | 89 | 1189 | [6] [M: *59] |
Notes: [C1] - Means code used for Cellular One service
[1] - for cellular in Pittsburgh, PA A/C 412 in some areas
[2] - indicates that you are not local and maybe how to reach you
[3] - found in Pac Bell territory; Intercom ring causes a distinctive ring to be generated on the current line; Hold keeps a call connected until another extension is picked up
[4] - applied once before each call
[5] - A.C.R. blocks calls from those who blocked Caller ID (used in C&P territory, for instance)
[6] - cancels further return attempts
[7] - *82 (1182) has been mandated to be the nationwide code for "Send CLID info regardless of the default setting on this phone line."
[M: *xx] - alternate code used for MLVP (multi-line variety package) by Telcordia Technologies, (formerly Bellcore). It goes by different names in different RBOCs. In Bellsouth it is called Prestige. It is an arrangement of ESSEX like features for single or small multiple line groups. The reason for different codes for some features in MLVP is that call-pickup is *8 in MLVP so all *8x codes are reassigned *5x
Under GTE, some LASS/CLASS tones may be changed from *NN to NN#. Under pulse, GTD5 allows either NN<pause> or 11NN, but with 11NN it may conflict with a test number.
Custom Local Area Signaling Services (CLASS) are PSTN telephony intelligent network services beyond basic voice calling, such as caller ID (automatic number identification (ANI)), caller number blocking, automated call return, call blocking or screening. Different IXCs offer various services. Late in the 20th century the term was simplified to LASS.
The services rely on the ITU-T standard Signalling System 7 (SS7) connectivity between network switches (SSPs) and databases (800 Database, LNPDB, LIDB, etc.) to operate. The CLASS standards were defined by Bellcore (now Telcordia Technologies) in the 1970s.
Some services such as call forwarding, three-way calling, call waiting, or speed dialing were sometimes condsidered part of custom calling rather than CLASS/LASS.
Source: Includes material from Federal Standard 1037C
