G.E.C. KEYPHONE 75
The GEC keyphone 75 pushbutton telephone is a direct replacement for rotary-dial telephones. It is suitable for step-by-step (Strowger), crossbar, and reed-relay exchanges, operating from normal loop-disconnect dial pulses.
No additional exchange equipment is needed: replace the rotary-dial telephone by the keyphone 75 and conversion to pushbutton working is complete.
With the growth of subscriber dialling for both national and international calls, codes inevitably contain an increasing number of digits - eighteen digits is the international maximum. In consequence, dialling becomes more laborious and more liable to error. With the keyphone 75, the subscriber can 'key in' the required number at the speed of thought and the likelihood of dialling errors is minimized.
The telephone is a GEC746 instrument in which a keyset and electronic store replaces the rotary dial. It has the same transmission performance as the GEC746 and, apart from the pushbutton circuits, uses the same parts. In addition, four switches can be fitted to give the operational features offered by the GEC740 switching telephone.
The number 'keyed in' via the keyset is held in the telephone within a storage unit which uses metal oxide semiconductor (MOS) integrated circuits. These circuits combine high reliability and low power consumption with small size.
The maximum of 18 digits can be stored. The store is sampled and a train of loop-disconnect pulses is transmitted to the exchange in accordance with the number 'keyed in'.
Electronic impulsing circuits and dry-reed relays permit very close control of impulse speed and ratio with negligible change in performance during life.
The telephone is line powered, from the exchange battery, with an additional small nickel-cadmium cell within the telephone to power the impulsing circuits during sending: this cell is recharged during conversation.
The keyset is a 10-button unit with button layout in accordance with CCITT recommendations. The buttons have a 'fall through' action to ensure positive operation; the contacts are gold plated and are enclosed in the keyset housing to provide protection against dust.
The GEC keyphone 75 pushbutton telephone provides an Administration with a quick and economic method of providing an up-to-the-minute pushbutton system without incurring high capital investment or adding specialized interface equipment between exchange and subscriber.
The GEC keyphone 75 pushbutton telephone is a GEC746 table telephone in which a 10-button keyset and an associated store/convertor unit replaces the rotary dial. It is suitable as a direct replacement for a rotary-dial telephone. The store/convertor accepts and stores up to 18 digits keyed in from the keyset and transmits them with appropriate inter-digit pauses as loop-disconnect (decadic) pulses to the exchange.
Store - accepts 18 digits keyed in as fast as the user wishes; metal-oxide
semiconductor (MOS) integrated circuits used.
Dimensions and weight
Take from The GEC-AEI Catalogue Leaflet DLT30A (Dated 1970)
Last revised: January 27, 2011