Frequency band J	11900-14250 MHz - later 11500-18000
Frequency band S	1650-5200 MHz - later 2500-4100
A2J	1kHz tone keyed sub carrier is added to TX synthesised frequency to produce A1
Frequency band K	20500-26500 MHz - later 18000-25000
Frequency band Q	33300-37500 MHz - later 25000-40000
Frequency band L	390-1650 MHz - later L2 300-1000 L1 1000-2000
Frequency band V	50000-75000 MHz - later 50000-74000
Frequency band X	5200-11900 MHz - later - C 4100-7000 X 7000-11500
A2 RATT	A Ratt system based on AF two tone shift keying using a UHF system in the DSB mode
ADCOCK	A system of folded dipoles for the D/F outfits FV series
Outfit letter PDA-PDZ	A.I.C. Outfits
Outfit letter DDA-DZZ	AC Supply outfits
ACI	Adjacent channel interference
ADCCP	Advanced data communications control procedure [ANSI]
ARPANET	Advanced research projects agency network
ASSATS	Advanced ship-shore automatic telegraphy system
AE	Aerial
Outfit letter KBA-KBZ	Aerial control outfits
Outfit letter EA-EZ	Aerial exchange outfits
Outfit letter ACA-AZZ	Aerial outfits
Outfit letter ESA-ESZ	Aerial switching outfits for radar
Outfit letter TA-TZ	Aerial trunk outfits
ATU	Aerial tuning unit
AMI	Alternate mark inversion
ANSI	American national standards institution
ASCII	American standard code for information interchange
M88	Amplifier unit for type 603 transmitter
M89	Amplifier unit for type 604/605 transmitters
AM	Amplitude modulation
AF	Audio frequency
Outfit letter RHR 1-6	Auto HS Receivers
Outfit letter RHT 1-6	Auto HS Transmitters
AFC	Automatic frequency control
AGC	Automatic gain control
AMRAD	Automatic message routeing and distribution system
ARQ	Automatic request for repetition
AVC	Automatic volume control
Type number 92-93	B.A.B.S. [Beam Approach Beacon System for aircraft]
CR100	B28 receiver - Marconi commercial design
CR200	B29 receiver - Marconi commercial design
Outfit letter Bac-BCz	Battery outfits
Type number 251-259	Beacons
BFO	Beat frequency oscillator
BSC [BiSync]	Binary synchronous communication [IBM]
BER	Bit error rate
BERT	Bit error rate testing
BWO	Bridge wireless office
BCA	Broadcast control authority
BSC	Broadcast Control Station
Outfit letter Group A/F	Bulkhead insulator
Type number 501-527	Buzzer Outfits
Outfit letter KDA-KDZ	C.W.S. [Central Wireless System] control outfits
CSMA/CD	Carrier sense multiple access with collision detection
TRIPLE-X	CCITT Recommendation X3, X28, X29
CCO	Central Communications Office
CCS	Central Control System
CPU	Central processor unit
CWS	Centralised Wireless System
COS	Change over switch
CARB	Channel availability and receipt broadcast
CRP	Character release pulse
CSF	Classified socket field
CUG	Close user group
CDMA	Code division multiple access
CODEC	Coder-Decoder
EAA-EAZ	Common aerial working outfits
CCR	Communications control room
CFC	Communications facility control
CR	Communications requirement
CRL	Contingency rear link
CW - A1	Continuous wave - Morse Code
Type number 203 & 5	Control of motor boats
CYO	Crypto office
XL	Crystal
XTAL	Crystal
XO	Crystal oscillator
CSU	Crytographic switching unit [Outfit PRC{1}]
CRC	Cyclic redundancy check
DCE	Data circuit - terminating equipment
DTE	Data terminal equipment
DCN	Defence communication network
DFTS	Defence fixed telecommunication system
DPSK	Differential phase shift keying
DDCMP	Digital data communications message protocol [DEC]
DDFS	Direct digital frequency synthesis
DNST	Directorate of naval shore telecommunications
DRS	Distributed resource system [ICL]
DSB - A3	Double side band voice
DPE	Dual path emission
EIRP	Effective isotropic radiate power
EVOS	Electronic voice operated switch
EWO	Electronic warfare office
ELTN	Engineering liaison teleprinter network
EOW	Engineering order wire
EDAC/EDC	Error detection and correction
CEPT	European conference of postal and telecommunications
EBCDIC	Extended binary coded decimal interchange code
Frequency EHF	Extremely high frequency 30 GHz - 300 GHz
Outfit letter KFA-KFZ	Fighter direction control outfits
FRF	Filter radio frequency
FCO	Fleet communications officer
FSCE	Fleet shore communication engineer
FSCO	Fleet shore communications officer
FAB	Frequency availability broadcast
FCS	Frequency calling schedule [HF Radio] - Frame check sequence [Data comms]
FDM	Frequency division multiplex
FDMA	Frequency division multiple access
FEK	Frequency exchange keying
FM	Frequency modulation
FSK	Frequency shift keying where the RF carrier is pulled up or down to achieve the shift.
FST - RN F1	Frequency shift telegraphy
FEP	Front end processor
GPTN	General purpose telephone network
GHz	GigaHertz
Type number 431-434	Hailers
HOA[N]	Harbour operations and administration net
HCP	Hard copy printer
Hz	Hertz
Type number 601-605	HF and MF transmitters
Outfit letter RH 1-3	HF D/F - rotating aerial
Outfit letter FH 3-5	HF D/F - fixed aerial
HDB3	High density bipolar - 3
Frequency HF	High frequency 3 to 30 MHz - Short Wave -in the RN usually 1.5 to 24 MHz
HF	High frequency 3 to 30 MHz - Short Wave -in the RN usually 1.5 to 24 MHz
HFEC	High frequency [radio] engineering control
HDLC	High level data link control
HT	High tension
IFF	Indicate friend or foe - radar systems
IVSN	Initial voice switched network
ITIMS	In-service transmission impairment measuring set
ICS	Integrated communications system
IDA	Integrated digital access
ISDN	Integrated services digital network
IDF	Intermediate distribution frame
IF	Intermediate frequency
Frequency IF [post war]	Intermediate frequency of a superhet receiver between the RF and AF stages
Frequency IF [pre war]	Intermediate frequency. In the 1930's this meant the 300-3000 kHz frequency band
IFRB	International frequency registration board
ISO	International organisation for standardisation
CCIR	International radio consultative committee
ITU	International telecommunications union
CCITT	International telegraph and telephone consultative committee
Type number 241-244	Interrogators
ICW	Interrupted carrier keying used when 602E is running on emergency power only.
Type number 249	Ionospheric sounder
ITL	Isolator, telegraph line
Type number 91	Jammer anti radar
kc/s	kilocycles [small letter 'k'] = kiloHertz [capital H because a mans name] today.
kHz	kiloHertz [always a small k]
LSI	Large scale integration
Outfit letter LAA-LAZ	Lighting arrestor for shore stations
LINCOMPEX	Linear Compression and expansion
LAP	Link access protocol
LAPB	Link access protocol [balanced]
LAN	Local area network
LCN	Local control Network [radio]/Logical channel number [X25]
LO	Local oscillator
Frequency LF	Low frequency 30 to 300 kHz [In the 1930's this meant all below 100 kHz] - Long Wave
LF	Low frequency 30 to 300 kHz [In the 1930's this meant all below 100 kHz] - Long Wave
Type number 610-616	Low power transmitters - transportable and portables
Type number 618-619	Low power transmitters - transportable and portables
Type number 681-687	Low power VHF
LPI	Low probability of intercept
LT	Low tension
LRR	Lower receiving room
LSB	Lower side band in an SSB system. Not normally used in the RN unless when ISB is used
LTR	Lower transmitting room
MCO	Main communications office
MDF	Main distribution frame
MSO	Main signal office
MWO	Main wireless office
MAP	Management processor [outfit PRB{1}]
MCCIS	Maritime communications, control and information systems
MHQ	Maritime headquarters
MRL	Maritime rear link
MO	Master oscillator
MTBF	Mean time between failures
MTTR	Mean time to repair
MF	Medium frequency [radio]/Multi Frequency [line]
Frequency MF	Medium frequency 300-3000 kHz - Medium Wave -RN usually 240 kHz to 3MHz
MHz	MegaHertz [always a capital letter].
MFRS	Message filing and retrieval system
MEP	Message processor [Outfit PRA{1}]
Outfit letter FM 1-15	MF D/F - fixed aerial
MSK	Minimum shift keying
MCW - A2	Modulated continuous wave - Morse Code using DSB [double sideband]
MODEM	Modulator/Demodulator
Outfit letter KMA-KMZ	Monitor and R/C outfits for YE and flying aids
MCVF	Multi channel voice frequency
NICS	NATO integrated communications system
NSTA	Naval shore telecommunications authority
NSTN	Naval shore telecommunications network
NTU	Network terminating unit
NUA	Network user address
NUI	Network user identity
NTE	Networking terminating equipment
NF	Noise Filter
NL	Noise Limiter
NRZ	Non return to zero
OTA	Off the air
OSI	Open systems interconnection
RX REC Socket	Output from the B40 RX's detector for disc or wire recorders
RX REB Socket	Output from the B40 RX's IF3 for photographic analysis of faults in transmission.
PAD	Packet assembler/dis-assembler
PSE	Packet switch exchange
PSS	Packet switch stream [BT]
PCC	Partial crystal control
PJF	Patching jack field
PEP	Peak envelope power
PLL	Phase locked loop
PRK	Phase reverse keying
PSK	Phase shift keying
PTT	Postal telegraph and telephone authority
PA	Power amplifier
PABX	Public automatic branch exchange
PSTN	Public switched telephone network
PAM	Pulse amplitude modulation
PCM	Pulse code modulation
PPM	Pulse position modulation
QPSK	Quadranture phase shift keying
QAM	Quadtanture amplitude modulation
Type number 531-537	R/C Outfits [Radar Control for aircraft]
R/C	Radar control outfits
Outfit letter JA-JZ	Radar indicator outfits
RIS	Radar interference suppressor
Outfit letter RIS 1-6	Radar interference suppressors
Outfit letter RTA-RTZ	Radar ranging outfits
Outfit letter HRA-HRZ	Radar teachers
Outfit letter RAA-RAZ	Radar training sight outfits
Type number 262-293	Radars
Type number 900-999	Radars
RATT	Radio automatic teletype
RCU	Radio control unit
RF	Radio frequency
Outfit letter RMA-RMZ	Radio maintenance room outfits
R/T	Radio telephone
RX	Receiver
Outfit letter CAA-CUZ	Receiver outfits less CEA, CEZ, CPA, CRZ which are radars
Outfit letter REA-REZ	Recording outfits