SECTION 518-310-401 Issue 2, January 1967 AT&TCo Standard

BELl SYSTEM PRACTICES Plant Series

227 A (MD) AND 2278 KEY TELEPHONE UNITS AUDIBLE AND VISUAL SIGNALING IDENTIFICATION AND CONNECTIONS • Rate the 227 A KTU ll'lanufacture Discontinued.

GENERAl

1.

This section is reissued to:

1.01

Since this reissue covers a general revision, arrows ordinarily used to indicate changes have been omitted.

1.02

• Include the 227B KTU. 2.

IDENTIFICATION

(S EVEN MODULES)

I-3·1/3Z

IN.l

______,,'c1!1 ''!1 (.

-

7

-

~~I

~ -!.

IN.

400A DIODES ~ACTORY

W IRED

Fig. 1 -

227A (MD) and 2278 KTU (Front View)

Fig. 2 -

227A (MD) and 2278 KTU (Rear View)

©American Telephone and Telegraph Company, 1967 Prin~d in U.S.A.

Page 1

SECTION 518·310-401

• Operating two or more signals which require different operating voltages.

PURPOSE

3.

To serve as a visual and audible signaling control, and switching relay for key telephone systems.

3.01

4.

DESIGN FEATURES

(a) Operates on 14 to 26 volts de. (b) 227B KTU- all wire spring relay contacts factory-connected to screw terminals on back panel. (c) 227B KTU- (CAl) and (CA2) relay windings are not commonly strapped within the unit as in the 227A KTU (MD). (d) Four 400A diodes factory-wired to provide four CAl leads. 5.

APPUCATION

• lA, lAl, 1A2, and 6A key telephone systems. • 2A communication system.

Fig. 5 - 227 A (MD) or 227B KTU- Multisignal Control for Ringers. • A power failure feature is provided by having the common or line signals, with capacitors, connected to the tip and ring of CO, PBX or private line while relays are unoperated. Fig. 6-227 A (MD) or 227B KTU- Common Audible or Station Audible for 6A Key Telephone System. Fig. 7 - 227 A (MD) or 227B KTU - Multisignal Control Circuit for Ringers Arranged for Combination of Audible Signal and Visual Signal. Fig. 8-227A (MD) or 227B KTU-Multisignal Control Circuit for Buzzers or Bells Arranged for Combination of Audible Signal with Visual Signal. Fig. 7 and 8 provide for:

• Key equipment No. lOlA or lOlB.

• Audible signal with locked-in visual signal. 6.

CONNECTION INDEX

• Locked-in visual signal can be released by manual operation of a SHUNT-DOWN key at called station.

Fig. 3 - 227A (MD) or 227B KTU- Auxiliary Lamp Relay Circuit. • Used when additional lamps over the maximum permitted for a given circuit are required. Fig. 4-227A (MD) or 227B KTU-Multisignal Control Circuit for Buzzers, Bells, or Ringers. Provides for: • Using the same audible signal as a line signal and common signal.

Fig. 9-227A KTU (MD) or 227B KTU with 228A or 265A KTU - Method of Connecting 400A Diodes for Additional CAl Leads. Connect CAl leads through 400A diodes when an audible signal is common to more than one group of line or signal circuits. This prevents false operation of audible signals not common to the same group of line or signal circuits.

6.01

CA leads may multiple to other CA leads, and CAl leads may multiple to other CAl leads if they are common to the same line or signal circuit.

6 .02

• Associating a common audible signal with one or more groups of line or signal circuits. • Operating one or more audible signals from one line or signal circuit.

Page 2

6.03

For additional information refer to SD-69294-01.

227A KTU IMD)

2278 KTU ONE REQUIRED P(R l GROUPS 0" 40 LAMitS PER LINE

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NOTES:

0

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--

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Fig. 3 - 227A (MD) or 2278 KTU -

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227A KTU (MD) or 2278 KTU with 228A or 265A KTU- Method of Connecting 400A Diodes for Additional CA 1 Leads