Telephone System In Electrical Construction Works



The contractor shall furnish and install a telephone system as specified herein and as shown in the drawings.


The following publications of the issues listed below, but referred to thereafter by basic designation only, form a part of this specification to the extend indicated by the reference thereto:



2.1 Rural Electrification Administration (REA) Publications:

  • PE - 22 April 1974  Fully color coded, Polyethylene or Crystalline Propylene/Ethylene Copolymer-Insulated, Polyethylene Jacketed Telephone Cables.
  • PE - 23 July 1973 Telephone Cables for Direct Burial.

2.2 American National Standards Institute Inc. (ANSI) Standards:

C2-1977 - National Electrical Safety Code.

2.3 National Fire Protection Association (NFPA) Standard:

70-1978 - National Electrical Code.


3.1 Coordination

The information drawings indicate the extent and general arrangement of equipment and the space and empty conduit system available for the telephone system installation. If any conflicts occur between the available facilities and the requirements of the telephone system which necessitate departures from the information drawings, details of such departures and reasons therefore shall be submitted with the proposal.

3.2 Operating Environment

The equipment provided shall operate under the following environmental conditions which will normally be maintained by the building heating, ventilation and air conditioning system.

1. Ambient temperature ±10 deg. C to 59 deg. C.

2. Relative humidity 20 to 50%.

3.2.1 Electrical Noise

The telephone system shall be protected from the introduction of noise from electromagnetic and electrostatic sources by grounding, shielding, trunk line filtering or other appropriate means. Potential sources of frequency radio and microwave radio.


3.3.1 Private Branch Exchange (PABX)

The PABX shall be of the latest design in architecture and digital technology using stored program control (SPC) and PCM format. Cross bar or any other electromechanical switching system will not be considered. The processor memory shall be restored automatically upon restoration of power following a total power failure. The system must be readily available and have been installed and commissioned in the state in a similar configuration to that requested by this specification.

3.3.2 Capacity

The capacity of the PABX shall be as follows:

Spare line slots shall be designed for single line dual tone multi frequency instruments.


  1. Initial: 60
  2. Growth potential to: 100

Central office trunks:

  1. Initial: 15
  2. Growth potential to: 25
  3. Percent incoming traffic: 30
  4. Percent outgoing traffic: 30
  5. Percent internal traffic: 40
  6. Dial tone delay: P-01
  7. Incoming traffic: P-01
  8. Outgoing traffic: P-01
  9. Internal traffic: P-05

3.3.3 Signaling:

The PABX shall be capable of receiving tone pulse signal from subscribers and transmitting dial pulse signals to the commercial network. The PBX shall be capable of interfacing with the local central office which has the following characteristics:

Loop start:

  1. 10 PPS dial pulse rate.
  2. 25 Hz, 60 to 80 Volt ringing signal.
  3. 5, 6, 7 digits to be received at central office for local calls.
  4. 8 - 15 digits to be received at central office for long distance calls.

3.3.4 Ringing Current and Tone Generation

Redundant ringing current and tone generator systems shall be provided with automatic transfer in the event of failure of the primary system.

3.3.5 Alarms

The equipment shall be provided with audio and visual alarms in the attendant area to annunciate normal power failure and over temperature. The audio alarms shall be capable of being silenced without correcting the malfunction. The visual alarms shall not be capable of being removed until the malfunction is corrected. Visual alarms only shall be provided in the attendant areas for all service effecting conditions.

3.3.6 Protection

All subscriber loops and central office trunks entering or leaving a building shall be protected against over voltage and over current.

3.3.7 Loop Resistance

Maximum subscriber loop resistance without telephone instrument shall be 1000 ohms.

3.3.8 Telephone System Maintenance

The PBX shall include an input/output terminal capable of changing the system program and initiating self diagnostic maintenance program.

3.3.9 Telephone System Features

The system shall be capable of providing the following features:

  1. Attendant conference - An attendant conference shall be able to establish a multi party conference call of upto six conferences.
  2. Attendant transfer - A subscriber participating in a two party shall be able to transfer the call or provide other assistance.
  3. Alpha numeric display - A four character display device mounted on the attendant console(s). Each character can display numbers (0 through 9), letter (a through z), and various miscellaneous symbols such as +/-. The display service display to attendant, and can be used for the incoming call identification feature.
  4. Automatic call back - If a subscriber calls a busy extension, he shall be able to activate automatic call back, hang up and be called back when the busy extension becomes idle.
  5. Busy lamp field - The attendant shall be provided with a visual indication of the status of all extensions
  6. Call forwarding - A subscriber shall be able to have all calls to his extension automatically forwarded to any other extension in the PBX.
  7. Call hold - A subscriber shall be able to hold an in progress call on his extension while calling a third party. The subscriber shall be able to confer privately with the third party, recall the first party thus establishing a three party conversation or activate another feature without establishing a three party conversation.
  8. Call pick up - Any subscriber in as assigned subscriber ground shall be able to answer an incoming call to any other subscriber within the group.
  9. Call waiting - If a busy extension is dialed, the called subscriber shall receive a tone indicating a caller is attempting to reach him.
  10. Manual exclusion - A subscriber shall be able to prevent a third party from entering into a call in progress.
  11. Flexible numbering - It shall be possible to reassign an extension number to another subscriber location without hardware modifications.
  12. Line lockout - If an extension is held off hock for a predetermined time without dialing or between digits the extension shall receive a warning tone and be held out of service without teeing up switching facilities. Line lockout shall be automatically released when the extension is returned to on hook status.
  13. Privacy - The attendant shall be prevented from entering an established connection unless recalled by a subscriber.
  14. Class off service - selected extension shall be restricted to placing calls only with in the PBX. Selected extensions shall be restricted to placing calls with in the PBX and non toll calls external to the PBX. The remaining extension shall have unrestricted service. The class of service assignment changed at any time to any modification.
  15. Night service - An attendant shall be able to select any common station line to receive all calls normally directed to the attendant.


3.4.1 Cables

Cable shall be made up of color coded, polyvinyl chloride insulated, solid annealed copper conductors with an overall polyvinyl chloride jacket.

3.4.2 Splicing and Termination

Direct splicing of cable will not be permitted. All splicing and terminating of cable shall be accomplished with plugs and connectors or connecting blocks as applicable.

3.4.3 Telephone Sets

  1. Normal telephone sets: Telephone sets shall be push button dual tone multi frequency type. Telephone sets shall be provided in the types and quantities specified. Exact telephone sets locations shall be directed by the consultant.
  2. Executive telephone sets: Executive telephone sets shall be hands free with display, memory and multi line capability telephone sets shall be provided in the type and quantities specified. Exact telephone set locations shall be directed by the consultant. The telephone set shall be NORTHEN TELECOM make type MERIDIAN, cat no. M2616.

3.4.4 Attendant console

One attendant console with busy lamp field shall be provided.


3.5.1 Cable installed overhead or in ducts shall conform to the requirements of REZ PE-22. The conductor shall be 0.95 sq. mm with copper conductor.

3.5.2 Splicing and termination: Splicing and terminating of exterior telephone cable shall conform to the requirement of REA PC-2.

3.5.3 Central office trunks: Central office trunks shall terminate on the main Distribution Frame.

3.5.4 Cable installation: The external cable shall be installed in PVC pipes. This shall be installed at a distance of minimum 30 cm away from the power cable. External access box with suitable cover shall be provided as shown in the drawing. No joints shall be made in the external cable. The termination of cable shall be done using proper terminal boxes of approved type.


An uninterruptedly power supply shall be provided consisting of battery charger, a static inverter, batteries, hardware, wire and battery mounting racks. The system shall support the operation of the telephone system for eight (8) hours following loss of normal power. The batteries shall be restored to full charge within eight (8) hours following restoration of normal power. Dual battery chargers and invertors with automatic transfer in the event of failure of any unit shall be provided.

3.6.1 AC power

AC power available is 220/127 volts, 3 phase, 60 Hz. The telephone system contractor shall be responsible for extending the branch circuit wiring from the source indicated to the rectifier.

3.6.2 Batteries

The batteries shall be nickel cadmium type.


Installation shall be accordance with NFPA 70 and ANSI C2 with exceptions only as modified by these specifications.

3.7.1 Cables shall be installed in conduits, cable trays, risers, floor trunking etc. already installed by the prime contractor. The contractor shall make provision for wiring all the telephone outlets shown in the drawing.

Where cables are placed on trays galvanized clamps shall be used within 150 mm of each termination. Galvanized clamps shall also be placed 50 to 100 mm in each direction from a turn or corner. When terminating cable, wire shall be supported so that no strain is imposed upon the conductors. Where wire must be extended from the wall to a desk along the floor, it shall be protected with floor duct or molding with proper fittings at each end.

3.7.2 Station equipment

Station equipment shall be installed in premises in dry locations indicated; however, no equipment shall be installed in any location hazardous to the user or injurious to the equipment. Wall type telephones or other station equipment shall not be mounted on damp walls. When mounted on uneven walls, wooden or plastic backboards shall be used. The backboard shall be mounted securely with appropriate mounting fasteners and the equipment mounted on the backboard without distortion of the base mounting plate of the equipment.

Station wiring and corks terminated in station equipment or on connecting blocks shall be free of strain at terminals, provided with sufficient slack for rearrangement, and formed so as to prevent interference in the operation of the equipment. No telephone set or other item of station equipment which has been damaged or which is found to be defective shall be installed. All telephone sets shall be equipped with a dial number card by means of a mechanical printing securely attached to the telephone set. Provision shall be made for Arab numerals also.


The telephone system shall be tested in accordance with contractor developed test plans. The test plans shall include in factory equipment tests prior to shipment, and system operation tests.


4.1 Cable Construction Work

Equipment installation work, connections and testing shall be performed by construction personnel who have had at least three years experience in this type of construction.

4.1.1 Communication cable

Splices and terminations shall be made by cable splicers who have minimum of 5 years experience in splicing and terminating communication cable.


Proof of personnel qualification shall be submitted to the consultant for approval no later than 30 days prior to the time work is to begin.


The contractor shall provide the consultant with two sets of circuit diagram books at the completion of construction. All printed material in the circuit books shall be typed and legible. The bound covers shall be printed and shall contain all required nomenclature relative to the material and the arrangement relative to the material and the arrangement of the books shall meet with the approval of the consultant prior to acceptance of the same.


The vendor shall certify that factory authorized service will be available in country for a period of one year after completion of the installation. The vendor shall, as part of the contract, instruct designated personnel in the complete operation and continue maintenance of the system.


7.1 Sufficient spare parts and maintenance material which shall be required for one year operation of the telephone system shall be supplied.

7.2 The vendor shall submit a list of the spare parts which are included.


The equipment to be furnished under this specification shall be guaranteed  for a period of one year from the date of acceptance thereof, either for beneficial use or final acceptance, whichever is earlier. Against defective material, design and workmanship, upon receipt of notice from the purchaser of failure of any part of the guarantee period, new replacement parts shall be furnished and installed promptly by the vendor at no additional cost to the purchaser.

The telephone equipment shall be NORTHEN TELECOM or ERICSON or AT&T make.