Prelude is a modern processor controlled voice switched loudspeaking telephone which can be wall or desk mounted.
Prelude is PST.

The facilities of Prelude are as follows-
  • Liquid crystal display which can show manual or hands free call, number called, time of day, call duration, programming information memory check, indicate tone signalling, prompt feature, alarm on or off and any empty memory locations.
  • On-Hook dialling and answering (i.e. handsfree use).
  • Mute. Pressing the "Secrecy Button" allows you to cut off the microphone, on both handset and handsfree calls.
  • Last number Redial.
  • Pause. Any number of 4 second pauses can be programmed.
  • Recall. Earth Loop or Timed Break (user switchable)
  • Dialling. LD (Pulse) or MF4 (Tone) Signalling (user switchable)
  • Mixed Signalling. If set for LD signalling pressing the '#' or Tone button will change signalling to MF4 until the call is cleared.
  • Ringer with Low, Off or High volume control.
  • Memory. 40 stores each with 25 digits capacity (pauses, TB recall, and signalling changes each count as a digit).
  • Battery protected memory.
  • Power unit (may improve LST performance under certain line conditions).

Made by Team Concepts International Ltd (Hong Kong)

BT supplied on sale terms only.

Approval Number S/1000/3/J/501107 for use on DELs and PBXs in categories l, 3, 5 & 7.

A 240 volts, 13 Amp, 50 Hertz Mains supply is required within reach if the Plug-Top power supply unit is used.

Ringer Equivalence Number (REN) of Prelude is 1

Approx. dimensions of Prelude, 220mm x 180mm x 80mm (or x 100mm with support stand fitted for desk mounted use). Weight (in packing) 1.5 Kg.

When Prelude is initially set up, the power switch should be set to LINE POWER. This will provide satisfactory operation of the loudspeech facility in the majority of cases.
Where loop-Line current is less than 30 milli amps in the LST mode or Prelude is on a long line LST performance may be improved by use of the Power unit supplied with Prelude, it this is used the switch must be set to MAINS POWER.

The signalling mode switches should be set on installation to:-
Tone + TBR - for Digital or Modernised exchanges and a minority of PBXs [i.e. PBXs requiring Timed break Recall).
Tone + Earth - for the majority of modern PBXs.
Pulse + Earth - for unmodernised exchanges and older PBXs.

Preludes are wall mounted by removing the wedge shaped support stand and using the key-hole slots on the base of Prelude. Wall mounting template and wall fixings supplied with the instrument.

Maintenance is limited to functional testing, checking switch settings, mains transformer unit output (if used - approximately 10 volts DC), loop line current (it less than approx. 30mA the power unit can be used and power switch set to 'mains power').
It is the users responsibility to replace the 3 AA size alkaline batteries at least once a year.
n.b. When the batteries are removed, all 40 memories clear and the clock will reset to 00.00.

Signalling details:
MF Tone signalling, continuous whilst keypad button is pressed.
Timed break recall, B5 milliseconds.
Earth recall, continuous whilst button is pressed.

RFI immunity:
Designed to give extra protection against RFI between 50kHz and 10mHz conducted and between 10MHz and 200MHz free field interference susceptibility.

The following field queries may arise with Prelude

  1. The Handsfree LST facility not working - check setting of power switch and power unit. Power switch must be set to 'Line power' if power unit is not used.
  2. Calls cutting off after 90 seconds - calls made by pressing a memory store button will automatically release after 30 Seconds unless user presses Handsfree button or lifts the handset (this is a safety feature of Prelude).
  3. Called party clears down - Calls made by pressing a memory button will be set up in the monitor mode, i.e. with the microphone `muted', this enable progress of call can be monitored without being affected by background noise but does result in no transmission to called party until the caller presses 'handsfree' or lifts the handset. Caller must press `handsfree' when caller answers.
  4. Batteries are not covered by warranty and replacement is customer's responsibility.
  5. No LCD display/delayed transmission - Batteries flat or not making contact.
  6. Batteries will not fit - Some brands of batteries may be a tight fit in prelude, Duracell batteries should fit satisfactorily.
  7. Timed Break recall problems in handset mode/display starting to fade - batteries due for replacement.
  8. Premature ring trip - Models with serial number below 90 360016100 incorporate a surge suppressor which may operate to high levels of ringing current. This depends on various factors including type of exchange/PBX, line length, line polarity. It may be overcome by reversing the line polarity or if a PBX checking ringing voltage is correct or by if a BT instrument by change out for a later model Prelude. The problem is less likely to occur on later models or those on digital exchanges, long lines or used with extension telephones.
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Last revised: December 18, 2010