BPO DIALS LIST

DIAL No 10		Standard dial, slipping cam type
DIAL No 11		As No 10, Used on prepayment coin boxes, has extra 
			contact set
DIAL No 12		Standard dial, trigger type
DIAL No 13		As No 12, Used on prepayment coin boxes, has extra 
			contact set
DIAL No 14		Used on testers
DIAL No 15		Used on testers, has additional break contact
DIAL No 17FA		Small figure dial for use on telephone No 280
DIAL No 17LA		Small lettered dial for use on telephone No 280
DIAL No 19		Telex dial, has changeover pulsing contacts
DIAL No 20LA		Used in director areas to allow prepayment coin 
			boxes to dial 100
DIAL No 21CA		Standard dial with coloured finger plate and arrowed ring
DIAL No 21FA clear	Standard dial with transparent figure plate and antique 
			silver ring with black numerals
DIAL No 1/21FA clear	As 21FA but low inertia mechanism, fitted to 
			telephone No 776
DIAL No 21FA steel	As 21FA but fitted with steel fingerplate, used on 
			public call offices
DIAL No 21LA black	Standard dial with black finger plate, used on 
			Telephone 1/232
DIAL No 22FA		Used on non director pre-payment coin box circuits, replaces 
			dial No 13
DIAL No 23FA		Used on director pre-payment coin box circuits, 
			replaces dial No 20
DIAL No 24FA		Telex dial has changeover pulsing contacts, 
			replaces dial No 19
DIAL No 25FA clear	As 21FA but with additional break contact, used 
			on 2/.. switchboards with PW's attached
DIAL No 25FT3		Used on testers, has 80% break and 12pps
DIAL No 25FT4		Used on testers, has 50% break and 12pps
DIAL No 26LA		Used on Flameproof telephones
DIAL No 28FA clear	Extra contact set only allows digit 9 to be dialled
DIAL No 30FA		Illuminated dial, used on telephone No 1/722.  The 
			fluorescent tube contains tritium, a radioactive gas 
DIAL No 35FA clear	Used on testers, has 66% break and 10pps, has 
			additional break contact
DIAL No 51		Standard dial of GEC design (alternative to dial No 21)
DIAL No 52		(alternative to dial No 21)
DIAL No 53		STC design (alternative to dial No 30 used on telephone No 722)
DIAL No 54a		Standard dial of EMI design

FA = Figures
LA = Numbers and letters

Last revised: January 28, 2023