TELEPHONE No. SA4258

Introduced around 1970 - high send level Trimphone for PABX's.

TELECOMMUNICATIONS INSTRUCTION
C MARKETING INSTALLATION
3 Internal
B3010
Issue 1, Mar 1972

TELE SA4258 KEYPHONES FOR PABX'S
WITH MF (SSMF4) SIGNALLING

GENERAL
This Instruction describes the 4 types of telephone which have been developed to meet the telephone requirements of PABX's having MF signalling capability. One instrument is based on Telephone 746, two are based on Telephone 740, and one based on Loudspeaking Telephone 4D. In each type of telephone the dial has been replaced by a Push-Button Unit No. 4... The push-button unit is associated with a multi-frequency line powered oscillator. When any button is fully depressed, two discrete frequencies are sent to line. There is a differing frequency combination depending on the button depressed.

As the number of spare telephone terminals available is less than in a normal 700 type telephone, an additional six way terminal strip has been provided. These terminals are numbered 20-25 inclusive.

As supplied, the telephones are not equipped to provide recall. This facility can be provided by fitting a Switch No. 5A-4 and associated press button assembly.

TYPES OF TELEPHONE
Telephone SA4258 This instrument is similar in appearance to the Telephone 746. It is primarily intended as a direct PABX extension, but can house 2 add on press buttons. A four way instrument cord and block terminal is supplied.

Telephone 2/SA4258 Similar in appearance to Telephone 740, this instrument is used when 3 or more press buttons a-re required. It is also fitted with two lamp opals and Lamp Fittings No. 16A. The lamp holder wires are terminated on terminals 20-24. Lamps are not included, but a suitable 12 volt 0.02 amp lamp is Lamp No. 48A. It is intended the lamps should be powered from a Power Unit No. 53A. A cord instrument is not supplied.

Telephone 4/SA4258 A wall mounting telephone suitable for direct cabling. It is electrically and mechanically identical to Telephone 2/SA4258. A wall mounting bracket is supplied with each telephone.

PUSH-BUTTON UNIT NO. 4....
Each type of telephone is fitted with a Push- Button Unit No. 4 .... The push-buttons are arranged in 3 columns of 4. The llth and 12th button tops are marked * and # respectively. The * and # buttons are required for providing additional facilities in the future, and serve no purpose at present. Depression of either of these push-buttons will send a combination of tones to line, but current PABX equipment will not respond to these signals.

The 2 variants of the Push-Button Unit No. 4 used on Telephone SA4258 are as follows:-

• PBU No. 4A is fitted in Telephones SA4258 and 2/SA4258
• PBU No. 4B is fitted in Telephones 4/SA4258

CONFIDENCE TONE
This is a combination of audio tones that can be heard in the receiver when a push-button is depressed. Its intention is to give the user an indication that the call is proceeding satisfactorily during the keying period. The tones will vary in frequency, depending on the button pressed.

DOCUMENTATION
Each of the telephone circuits, together with the extension plans in which Telephone .... /SA4258 may be used, is shown in Diagram SA(L)4258. It should be noted that all extension plan titles are prefixed by the letters K MF, i.e. Plan 107 becomes Plan K MF 107. This is to prevent confusion with orthodox extension plans. The K MF denotes that a keyphone is being used, using a multi-frequency signalling principle.

The above diagrams are not available through general circulation. If required, requisitions should be submitted in the normal manner.

ADDITIONAL INFORMATION

Last revised: November 20, 2007

FM