The Catacombs The Continuity Guide
by Martin Willey


With comments by Marcus Lindroos

The Infernal Machine Alpha Child The Troubled Spirit

Each Alphan has a commlock, providing internal communications and access to areas of the base. The name is normally spelt "commlock" in scripts and production material. On-screen it is "commlock" in Guardian Of Piri, but "comlock" on the test card screen in The Immunity Syndrome. The "Emergency Procedure" notices, just readable in some shots (such as Space Warp), also say "comlock".

Alpha Child The Immunity Syndrome

The commlocks have similar capabilities as the stationary communications posts (i.e. internal microphone + loudspeakers + camera + small display for voice activated audio/video call and remote access to external computer and video service providers; "security alert" alarm button [Matter of Life and Death], lunar chronograph [Earthbound]), but additionally emit an electronic ID "door key" signal as well as a locator beam [Matter of Life and Death, Death's Other Dominion] for tracking purposes. Main Mission can call all wireless commlocks and/or fixed communications posts in a given area (End of Eternity) and the overall communications network is managed by Alpha main computer (Guardian of Piri).

Another Time, Another Place

Front view of the commlock. Note its somewhat worn appearance.

Commlocks are used internally in Moonbase Alpha, on the lunar surface (around Alpha and in the Nuclear Waste Disposal Areas), and on space missions- not just on Eagle flights from Moonbase Alpha, but used by the crew in the 1996 Ultra Probe mission (Dragon's Domain).

Breakaway Black Sun Force Of Life

They are normally worn on the belt or on the side of spacesuit chest packs (Breakaway only). They may be stored in a desk-top stand (Black Sun, Alpha Child; the stand is presumably also used for recharging the power cell and possibly direct cable transfer of data to Alpha main computer (similar to a smartphone docking station).

Alpha Child Alpha Child
Black Sun Black Sun

The commlock can be used in pressurized areas as well as in the vacuum of space (it seems to be watertight, e.g. The Rules of Luton) and also in arctic conditions (Death's Other Dominion); however, it will not work in highly radioactive areas (Mission of the Darians). Crews wearing spacesuits presumably use the commlock as a remote control for controlling the helmet microphone + earphones (see e.g. Space Warp); the commlock's internal audio capabilities would be useless in the vacuum of space.

Access control

The commlock can be used to open doors remotely. It is functionally identical to the remote keyless systems used in cars since the 1990s. The commlock may be like the car key fob which emits a radio frequency with a unique digital identity code. Alternatively it may use a near-field communication (NFC) technology with a more sophisticated electronic key, as used by modern smartphones.


Doors are opened by aiming the barrel at the door and pressing any key. In Force of Life, Zoref aims the commlock screen instead so there are presumably two ports.

Computer panels can also be opened (Earthbound, Guardian Of Piri) and the laser barrier at NDA 2 (Breakaway). Commlocks are often stolen to provide access (Earthbound, Alpha Child, Dragon's Domain).


If user password protection is available, Koenig's somewhat embarrassed request to Kano in Earthbound ("Deactivate that commlock. And have Computer program an alternative command commlock for me. Explain to the Computer as best you can") suggests all commlock owners do not bother to use this feature. It seems Alpha's central computer interprets requests to open or lock all/some doors based on the identity of the commlock as well as its location vs. the nearest door (Collision Course, Beta Cloud). The commlock occasionally acts as a "doorbell" alerting office or living quarter occupants that a visitor is waiting outside, requesting permission to enter (Breakaway, End of Eternity, Alpha Child, Matter of Life and Death).

Commlocks are rarely used for opening / closing doors in Year 2 except in space (e.g. Eagle passenger module door in All That Glisters, nuclear area doors in Bringers of Wonder part 2). The "door open" keytone is also slightly different. Inside Moonbase, most Year 2 doors either open automatically or by pushing the door access keys. If the commlock is used at all, it is mostly for issuing voice commands to Main Computer to open/close a particular door (in Beta Cloud).

Audio/Visual Communications

Breakaway Matter Of Life And Death Matter Of Life And Death Earthbound Space Brain The Rules Of Luton

For communications the commlocks have a speaker/microphone grill and a small black and white screen (it is colour in The Rules Of Luton) and cameras (a front camera by the screen, for 2 way face communication, and in some episodes in the barrel).

Devil's Planet

In Devil's Planet the barrel is aimed at the subject to be filmed so the unit presumably has two cameras

The close-ups of the screen use a slightly larger prop (to fit the 1.5"/35mm screen of the Panasonic TR-001, with a connecting cable held out of sight). The screen is shown frequently in Year One, but in only two episodes in Year Two: The Rules Of Luton (the colour screen) and The Immunity Syndrome.

Matter Of Life And Death

This close up in Matter of Life and Death is a larger screen again. The black enclosure looks like the commlock, but it is set in a blank vertical wall, with no attempt to make a commlock body.


The hood around the screen is sometimes reversed, with the higher side towards the back. This is often inconsistent between scenes (as actors used different props on different days). By the time Bergman arrives in Main Mission, the hood has swapped back to the regular side.

Unlike current webcams or 3G cell phones, the video image broadcast by the commlock is not shown on the internal screen as well (i.e. it is only broadcast to the receiving commlock or video monitor). This would make it harder for the user to ensure his/her face is correctly positioned and visible to the camera. However, it is possible that the system has a built-in "face tracking"/autofocus function much like current computer webcams do. You can receive video calls without sending video back, as demonstrated in The Full Circle when Spearman receives the call but does not transmit his image.

UI: Buttons and Operation

It seems the commlock user interface (voice commands, single-key push-to-talk operation, anykey answer, anykey operation of the "door open" ID signal) is designed for convenient use by astronauts wearing thick spacesuit gloves. The unit has more than 20 buttons, so the risk of accidentally activating a commlock function would be great without a default "lock keypad" mode (possibly, only the "door open" signal is emitted if any key is pushed while the keypad is locked). The buttons on the side of the unit are unlabelled; they are presumably user definable function keys.

Matter Of Life And Death

The numeric keypad on front face of the unit provides quick access to other commlocks or computer services (the number keys perform different functions in different episodes, so they are presumably programmable "speed dial" buttons). On most commlocks the buttons are flat (actually just stickers). Only the larger scale TV prop and two other "hero" props had raised keys. These raised keys are fixed- they do no depress when touched. The others, including the normal props seen being used by Koenig and Helena, and often props seen in close-up, had flat buttons.

The Immunity Syndrome The Immunity Syndrome

This "crushed commlock" from The Immunity Syndrome is a poor prop, but most prop commlocks have flat buttons like this.

Black Sun

Sometimes the numeric buttons on the front of the keyboard are not numbered. Both Helena and Sandra's buttons are unmarked. Note that the screen hood on the top of the commlock face opposite directions (thanks to Glenn McCrabb).


Koenig's commlock has unnumbered buttons sometimes, as here in Breakaway (earlier in the sequence, in Main Mission, his commlock did have numbers). The "wonky buttons" version of his commlock (see below) had no numbers.

The Beta Cloud The Beta Cloud End Of Eternity

While the commlock communications are normally operated with the keyboard on the top face, occasionally it is used "upside down" or even sideways. Presumably the device detects this and inverts the screen and camera image. Sometimes, the operator does not even bother to look at the screen, e.g. Dr.Russell calls security in Missing Link without removing her commlock from the belt. This suggests the device can be used for making audio-only calls (with the video camera turned off) as well as audio/video.

The Immunity Syndrome The Immunity Syndrome

These shots show how commlocks are normally held. Koenig usually has his thumb on the angled grille, as if it was a button. This hold has a risk of accidentally pressing buttons.

The Immunity Syndrome The Immunity Syndrome The Immunity Syndrome

The unique way of holding a commlock is used just twice, in The Immunity Syndrome. It has the advantage of avoiding hand injuries if the keyboard explodes (which, both times, it does).

The Emergency Procedure signs in Moonbase and Eagles state "In the advent of an emergency press red button on side B of your comlock." This opens the panel with the lever controlling the escape hatchways. The red button must be the button over the numeric keypad on the front face of the commlock.

Alphanumeric keyboards have proved to be unpopular for most real-world phones, mainly because of the small size. The huge popularity of SMS ("texting") has been enabled by predictive text and word completion systems on numeric keypads; the 26 letters are assigned to letters 2-9. The commlock only has numbers 1-9 on the numeric keypad (there is no 0), which would be sufficient for text entry using modern predictive text (the other buttons may be used for punctuation, casing and toggling predictive text).

The Full Circle

Most commlock calls seem to be "push to talk": voice commands are interpreted by speech recognition system (probably in Alpha's central computer rather than in the commlock itself), to direct the call to the correct commlock. The Full Circle suggests that the commlock can be used either in push-to-talk "walkie talkie" or telephone mode (Sandra initially uses the PTT option before finally trying to make a phone call to Alan's commlock when he does not respond). It also seems that the commlock has a radio receiver for picking up analog radio transmissions, such as Dr.Rowland's in Death's Other Dominion.

It seems the speaker/microphone area to the right of the screen is touch sensitive. Koenig in particular prefers to operate his commlock by pushing these keys, which apparently provide convenient "hotkey" access to conference call functions (last received call, last dialled call, hold/mute etc.) for quickly switching from one caller to another, see e.g. Matter of Life and Death. Presumably, the status and actions performed by these buttons can be displayed on the adjacent commlock screen.

Other Features


The commlock can also be used as a remote control for displaying computer data on the communications post screens (Breakaway, Black Sun). In Alpha Child Jarak uses the commlock as a handheld microphone while the video link is provided by a communications post in Medical Centre. In Testament Of Arkadia, Koenig uses the commlock as a remote control to answer a commpost video call from Kano and later to make a commpost video call to Paul Morrow. In Troubled Spirit, Dr.Russell pushes a button on her commlock to turn out the lights in Dan Mateo's medical ward.

Planetary exploration teams sometimes use the commlock screen for displaying live video from surveillance cameras on the surface, Eagle Transporter cockpit etc. (Matter of Life and Death). It seems logical to assume that the commlock screen also can display vital spacesuit status related information such as oxygen and battery power level.

Other features include showing lunar time (Earthbound), a security alert alarm (activated by pushing the right-side silver button in Matter Of Life And Death , though not used in A Matter Of Balance or Space Warp when wall alarm buttons are preferred), and for Koenig to talk to computer (Guardian Of Piri, Alpha Child, Collision Course, Dragon's Domain, The Bringers Of Wonder part 2).

Seed Of Destruction

The commlock loudspeaker can be reprogrammed to emit high frequency sound (Seed Of Destruction). The device occasionally makes a beeping sound when making as well as ending a call, but this (as well as the incoming call ringtone) is presumably a user definable function. Interestingly, all commlock calls use the internal loudspeaker (there does not seem to be a telephone earpiece for private conversation) although astronauts on extravehicular "spacewalks" clearly use a wireless headset.


Click for larger image

Each commlock bears a photograph of the owner.

Ring Around The Moon

In Ring Around The Moon it occupies the whole of the side of the commlock

Missing Link

In Missing Link, Koenig's photo is sideways

Bergman's commlock

The worn Letraset lettering under the picture is visible here: "Registered Trade Mark. Letraset Products are prote-". Note the numbers on the keypad are also badly worn.


In Earthbound, Simmonds steals Koenig's commlock. In some scenes, he is wearing Bergman's commlock. Guest stars sometimes have recycled commlocks with the photos of previous owners.

Koenig's commlock is often missing button 1 from Matter Of Life And Death to Collision Course.


Koenig's buttons have shifted all over the place. This happens in many shots from Earthbound to Collision Course.

Alpha Child Another Time, Another Place Guardian Of Piri The Last Sunset The Last Sunset Collision Course

The "wonky buttons" commlock is often clearly visible on screen, including these shots.

Collision Course

Kate seems to have borrowed Koenig's commlock.

Alpha Child Collision Course

Helena loses her button 1 in Alpha Child, Collision Course and The Troubled Spirit.

Force Of Life Force Of Life

The commlock with missing button 1 also appears for other Alphans.

A Matter Of Balance

A stunt commlock- we see this crude prop for a few frames before Koenig throws it across the set in A Matter Of Balance

Belt clip

Dragon's Domain

The commlock has a clip at the back which is tucked into the belt, normally on the left hand side. Increasingly through the series, Koenig grabs his commlock when he descends the Main Mission steps, perhaps to stop it falling out the belt.

Ring Around The Moon

Starting in Ring Around The Moon, Helena's commlock hangs further out from the belt, and much lower. As this shot shows, behind her commlock is a strap around her belt. The strap has a hook, into which Helena slots the commlock clip. See more information

Technical Discussion

It is not clear from the episodes what the commlock's operating range is. In War Games, Koenig (assisted by the aliens?) is able to contact Paul's Eagle from the surface of the planet whereas in The Last Sunset, no attempt is made to contact a rescue Eagle passing directly overhead (perhaps the commlocks were non-operational?). The commlock presumably has an omnidirectional antenna; the barrel would seem to be the logical location for this. If the transmitter has a mobile phone-like output of a few watts, the commlock would be capable of sending/receiving real time video (~tens of thousands of kilobits per second) over a distance of a few tens of kilometres, consequently a relay station would be required for communicating with Moonbase Alpha. This is presumably how Koenig manages to have a video conversation with Dr.Bergman from Terra Nova in Matter of Life And Death. Direct audio phone calls (which require a transmission rate of a few thousand kilobits per second) to spacecraft might only just be possible, if the receiving spacecraft is relatively close and carries a large enough antenna. The scene in Earthbound where Alpha manages to pick up faint signals from Simmonds's commlock thus seems realistic. Notably, Simmonds apparently expects his commlock power cell to last the entire trip to Earth (70 years!) but this might be yet another indication that the commissioner is not well informed about technology.

The commlock is one of Keith Wilson's best known and most enduring designs for Space:1999. The original prop was designed around what then was "the world's smallest TV screen" (the 1971 "Integrated Circuit" Panasonic TR-001, 1.5"/35mm across). Ironically, the prop's sole working feature has been obsolete for decades (cathode ray tube TV displays are too bulky and consume too much power for mobile applications) but the commlock itself managed to anticipate the future remarkably well.

Commlock and Nokia 9000

The commlock makes its first appearance in the flashback episode Dragon's Domain which was set in 1996 (it also seems to be at least somewhat compatible with the Uranus probe radio transmitter from the mid-1980s in Death's Other Dominion). The same year, Nokia released its highly successful Nokia Communicator 9000 cellphone. It did provide mobile data access services and a small alphanumeric keyboard, but video telephony was only introduced in 2003 with the advent of the first 3G cellphones so the commlock was slightly ahead of its time. Current cellular telephones have many features anticipated in 1973, including audio-only and audio/video call capability, computer network access plus built-in infrared ports and short-range radio (Bluetooth) for communicating with external devices. In 2003, a U.S. company (Vocera) started offering a WLAN based commlock-like mobile push-to-talk system which has proven quite popular with American hospitals. It allows users to instantly contact other individuals (including unnamed ones such as the guard or nurse on duty) without having to dial a number; the system uses simple voice commands instead.

A commlock appears in an episode of the science fiction series For All Mankind (shown 9th April 2021).

Copyright Martin Willey