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First posted Aug 31, 2015
Last update Apr 13, 2016
WE-400B.jpg 153.1K WE 400 B CO or PBX Lne Circuit
See BSP SECTION 518-215-400 from the BellSystemPractices.org website.
The 400-type KTUs are 4-inch 18-contact units used to provide a key telephone set with CO or PBX line services. Pickup and hold of a CO or PBX line. Flashing line lamp on incoming call. Audible line signal and/or common audible signal on incoming call. Steady lamp indicating busy condition. Steady or winking lamp indicating hold condition. Talking circuit connection to CO or PBX line maintained during periods of power failure. Individual line time-out on unanswered incoming calls with different timing interval options. Delayed hold release
WE-400C.jpg 137.0K WE 400 C CO or PBX Lne Circuit
See BSP SECTION 518-215-400 from the BellSystemPractices.org website.
Updated version with more features
WE-400D.jpg 131.9K WE 400 D CO or PBX Lne Circuit
See BSP SECTION 518-215-400 from the BellSystemPractices.org website.
The 400 D KTUs are similar to the 400 C series but with updated features and more robust reliability.
WE-400G.jpg 183.6K WE 400 G CO or PBX Lne Circuit
See BSP SECTION 518-215-400 from the BellSystemPractices.org website.
WE-400H.jpg 137.2K WE 400 H CO or PBX Lne Circuit
See BSP SECTION 518-215-400 from the BellSystemPractices.org website.
The last 400 series version produced by Western Electric. Mostly solid state with only 2 mercury wetted relays. These KTUs tended to be burned out more frequently than the earlier versions due to voltage spikes.
ITT-400TPL.jpg 166.0K ITT 400 TPL
ITT Practice 36-400-202
These line cards isolate the customer's inside wiring from the incoming CO lines and made it possible for privately owned key telephone systems to avoid renting Voice Connecting Arrangements from the serving Bell Operating Company. These KTUs supply loop current to the stations instead of their receiving it directly from the CO, repeat outgoing dial pulses to the CO instead of their passing directly through the KTU as with conventional 400-type KTUs, and regenerate ringing from a local customer-owned ringing generator. (curt Steph Kerman)
WE-401A.jpg 100.5K WE 401 A Manual Intercom line Circuit
See BSP SECTION 518-215-400 from the BellSystemPractices.org website.
The 401A KTU (Fig. 3) is a 4-inch, 18-contact unit that provides talking battery for manual intercom and control for line busy lamp feature. Audible signaling between stations is accomplished by means of separately furnished pushbuttons, buzzers, or bells.
WE-401B.jpg 119.5K WE 401 B Manual Intercom line Circuit
See BSP SECTION 518-215-400 from the BellSystemPractices.org website.
The 401 B KTUs are similar to the 400 A series but with more robust reliability.
KE-403A.jpg 117.4K ITT 403 A Music on hold
The 403A KTU provides the interface to connect a low-level music source such as a tape deck or FM tuner to a CO/PBX line when placed on hold. The 403A KTU will serve a maximum of six CO/PBX lines. It mounts into a separate card panel adapter.
WE-412A.jpg 154.5K WE 412 A Auxiliary Relay Circuit
See BSP SECTION 518-215-403 from the BellSystemPractices.org website.
The 412A KTU is for use as a panel slave relay to augment signal interrupter lamp capacity for large installations. The KTU is arranged to plug into 584-type panels. It contains four de operated mercury relays for lamp flash or lamp wink control. Each relay can control a maximum of one hundred 51A- or 53A-type lamps. Each relay is also arranged so that it may be controlled individually. Coils are provided with protection networks.
WE-413A.jpg 120.6K WE 413 A Auxiliary Ringup Circuit
See BSP SECTION 518-215-403 from the BellSystemPractices.org website.
The 413A KTU is a 4-inch, 18-contact unit providing an auxiliary nonlocking ring detector for use on CO or PBX lines supplying either 20- or 30-Hz ringing voltage. Contacts of the ringup relay can be used for controlling external signaling functions or relays.
WE-415A.jpg 136.4K WE 415 A Automatic, DC Signaling, Private Line Circuit
The 415A KTU is a 4-inch, 18-contact unit for connecting a telephone set to a private line terminated at a distant location. Another 415A KTU, or other tie line KTU which will respond to a DC signal, is required at the distant location. The distant telephone set is automatically signaled when the line key on the local telephone set is operated and the handset is lifted. The 415A KTU provides a talking and signaling circuit with the same operating features as the 414A KTU and, in addition, provides: Optional lamp wink as an indication of hold. Ringing ranges with -20 volt battery supply are shown in Table H.
KL-416A.jpg 138.4K WE 416 A Station Lne Circuit
See BSP SECTION 518-215-403 from the BellSystemPractices.org website.
The 416A KTU is a 4-inch, 20-contact unit for connecting a private line between a local telephone set and a telephone set at a distant location. A nonlocking key, in addition to the line pickup key at the local telephone set, is required to operate the audible signal at the distant station. The local station is signaled by lifting the handset and operating the line key associated with the set at the distant location.
WE-417.jpg 130.2K WE 417 A Add-on Conference Circuit
See BSP SECTION 518-215-403 from the BellSystemPractices.org website.
The 417A KTU is a 4-inch, 40-contact unit that provides for bridging of two lines for a 3-way conference in the following arrangements: (a) A CO line and a PBX line (b) Two PBX lines or two CO lines (c) A CO or PBX line and an intercom line.
WE-418A.jpg 145.9K WE 418 A Short Range, DC Signaling, Private Line Circuit
See BSP SECTION 518-215-400 from the BellSystemPractices.org website.
The 418A KTU is a 4-inch, 20-contact unit for connecting a private line between two telephone sets, usually on the same premises. A single KTU will serve two stations. The unit may be connected for one of three methods of signaling: two-way automatic, two-way manual, or automatic one-way and manual one-way.
WE-420A.jpg 157.7K WE 420 A Dial Intercom Long Line
See BSP SECTION 518-215-402 from the BellSystemPractices.org website.
Provides a circuit for use with off-premise stations connected to the dial selective intercom line circuit. This KTU extends the loop resistance of the basic selector to 500 ohms. No provision is made for busy lamps at stations connected to this circuit. Mutilation of other station dial pulses is prevented by relay operation. The KTU provides the following operating features: Signaling and talking over single pair from off-premise stations. Any code may be assigned to off-premise stations. Ringing can be tripped only during silent intervals.
WE-421A.jpg 129.5K WE 421 A Power Failure Transfer Circuit, Audible Signal Suppression Circuit, or General Purpose Relay
See BSP SECTION 518-215-403 from the BellSystemPractices.org website.
The 421A KTU is a 4-inch, 40-contact unit that can be used to automatically transfer a maximum of three station ringers from a common audible connection to a line ringing connection in the event of a power failure. It can be used to suppress (cut off) audible signals on a line or lines associated with a key telephone set when that set is off-hook. It can also be used as a general purpose relay.
WE-429B.jpg 139.9K WE 429 B Supplementary Hold Detector Circuit
See BSP SECTION 518-215-401 from the BellSystemPractices.org website.
(Used in conjunction with a 430A KTU (Flutter Generator Circuit) These KTUs together provide an adjustable lamp flutter of approximately 12 interruptions per second to indicate a supplementary hold condition as distinguished from lamp wink or steady signal associated with a normal hold condition. (Reference 'Priority Hold' and 'I Hold')
WE-449A.jpg 149.6K WE 449 A Immediate Transfer Control Circuit)
See BSP SECTION 518-215-403 from the BellSystemPractices.org website.
The 449A KTU consists of two identical circuits mounted on a 4-inch printed wiring board. Each circuit consists of an electrical flip-flop which provides immediate transfer of ringing. The flip-flop is activated by a nonlocking key located at the principal station. When the key is operated, the flip-flop locks up to transfer incoming ringing from the principal station to the attendant station. A steady lamp indication is provided at the principal station when the nonlocking key is operated and the flip-flop is locked up. The transfer is canceled by operating the nonlocking control key a second time.
WE-451B.jpg 135.8K WE 451 B Music-On-Hold
See BSP SECTION 518-215-401 from the BellSystemPractices.org website.
The 451B KTU is a 4-inch, 40-contact unit that provides music-on-hold to CO/PBX line circuits. The 451B KTU transmits music to distant stations that are placed on hold by users of this system. The KTU contains seven identical circuits, each of which may provide music-on-hold to one CO/PBX line circuit. The music source should have an adjustable volume control so that the listening level of the music may be adjusted.
WE-455A.jpg 133.2K WE 455 A Tone Ringing Signal Geneartor
See BSP SECTION 518-450-100 for basic information
The 455A KTU is a 4-inch unit that contains the tone ringing generator for CO/PBX signaling used in conjunction with a 7A communication system.
WE-457C.jpg 137.1K WE 457 C Paging Amplifier for the 14A Com Key system
The 457C KTU unit contains the paging amplifier circuitry for paging and for customer-provided background music. The customer-provided music source can be connected to the paging speakers while the paging circuit is not in use. Three 457C KTUs can be used in the 14A System and seven loudspeakers can be connected to each unit. For paging, each 457C KTU may be accessed by a separate intercom code (for zone paging) or one intercom code may activate a combination of units. The 457C KTUs occupy connectors J28, J30, and J32 in the 580-type KSU. The output of the 457C KTU is 3 watts of peak power.
WE-461A.jpg 148.5K WE 461 A Manual Signaling, Ringdown Private Line
The 461A KTU (Fig. 15) is an 18-contact version of the 414A KTU. The spare contact available on the 414A has been eliminated and B ground used for RG. Another tie line circuit KTU is required at the distant location. A nonlocking key on the telephone set, or an externally mounted key in addition to the line pickup key, is required for signaling. The 461A KTU provides a talking and manual signaling circuit with the following operating features: Flashing line lamp on an incoming calL. Steady lamp indicating line busy. Time-out on unanswered incoming calls; optional time intervals. Choice of audible signals: common audible, steady, or interrupted. Audible ringback signal option so calling party can hear a tone from the distant telephone.
ITT-10-StationIntercom.jpg 170.5K ITT 183981-101 10 Station Dial Intercom
One component in the Announce-a-Call intercom system which is designed for use in 1A2-type key telephone systems to provide dial-selective Intercom. It provides a single common talking path for all stations in a system and 2-digit dial selection of and signaling. The standard unit provides 10-statlon rotary-dial intercom with dial tone and ringback to the calling station plus Intermittent signaling at the called station when ringers are used or call announcing with handsfree answerback when Call Announcers or telephones with built-in call announcer are used. Ringer stations and callannouncer stations may be mixed in a system with half of the station capacity allocated to each method of signaling.
GTE-1400F.jpg 134.8K GTE 1400 F Music on hold line card