BID 100 (Hallmark)
This description is taken from the User Handbook (Second Trials Edition) for BID 100 and was provided by Chris Suslowicz. HALLMARK is the British War Office designator for the device and BID 100 is the Ministry of Supply name for the same equipment.

BID 100, circa 1954, is a single channel speech cipher system which secures point-to-point telephone lines and radio links. The equipment operates from a special  telephone exchange and is not intended for use through a public telephone facilities. Up to 5 miles of quad cable or a radio link may be used between BID 100 terminals. The radio link, however,  must have a transmission bandwidth from 500 Hz to 30 kHz.  A suitable radio for this task is the WS B70. When cable is used, such as 'P' type quad wire, the typical communication distance is 5 miles.  The manual also quotes 10 miles without any other qualifiers but perhaps this is the maximum distance under ideal conditions.

There are two modes of operation for the terminal - simplex ("over-over operation") or full duplex. The signal being passed over the link is in the form of alternating binary pulses representing the enciphered Pulse Code Modulation signals. BID 100 requires no special starting procedure since the required synchronization is done automatically on the receiving terminal. Even if there is a break in the transmission, the system will synchronize itself within a fraction of a second once transmission is resumed.

Facilities are provided for up to 5 telephone extensions at either terminal by means of a special switchboard unit. This switchboard unit together with its 5 way quad coupler line extension box was still under development in July 1954.


The BID 100 comprises of two main units: a Pulse Code Modulator (PCM) unit and a Waveform Generator (WFG) unit, each having its own power supply. It is necessary to have two WFG units in order to carry out the initial setup procedure, even though the station may eventually be used for SIMPLEX operation only. In that case, the second WFG is retained as a spare.

The PCM unit incorporates the circuits for converting speech signals into a suitable form for enciphering prior to transmission and for converting the received and deciphered signals back into speech. It also contains the oscillators for timing the operation of these circuits.  Also included are circuits for converting the outgoing signals into a suitable form for transmission or the cable or radio links and for the reception and regeneration of signals at the receiving end of the link.

The WFG unit consists of four "book" assemblies in positions A, B, C, and D. Books in positions A, B, C are used for enciphering and deciphering. Book D carries all external connections for the input and output pulse regenerator stations.

For SIMPLEX operation, a terminal consists of a PCM unit and a WFG unit which are connected together by means of a short interconnecting cable. Provision is also made for external connections to the telephone unit or switchboard unit for the quad cable. For FULL DUPLEX operation two WFG's are required for each terminal .


The BID 100 equipment operates from 110/120 or 200/250 VAC mains, 45 to 65 Hz. Each Waveform Generator consumes 200 watts and the Pulse Code Modulator is 150 watts. The special switchboard operates on 24 VDC (two 12 volt batteries in series).


WFG unit in transit case  146 20.5 27.5 16
PCM unit in transit case  112 20.5 17.5 16
Telephone unit in transit case  7.25 11 6 6
Line coupler 4 7 6 3.75
Telephone extension coupler  4.5 11 4 7
Switchboard in transit case  47 20.5 10.5 16
Spares box 28 15.25 8.75 13.75

At the right is the BID100 with one Pulse Code Modulator (top) and two Waveform Generators (bottom). The operator is using the Telephone Exchange.
Close up of the Telephone Exchange. 
The HALLMARK telephone.
This LCV lorry (3 ton) was used to transport BID100. It occupied the front compartment. 
bid100_report .jpg
This is the report cover for the Field Study of the BID100 use with the WS B70 radio.
All materials courtesy of the British Army. Photographed by  Chris Suslowicz 


Front view
Side view
The dimensions of the radio set are: 17"W x 13"H x 8"D. Weight is 20 kg.
Rear view. The dishes are 16 inches in diameter and are detachable.
Various views of the WS B70 microwave link.  The radio is missing the power supply. (All photos courtesy E-bay)

The Condition Indicator was used  to check the output power level of  the SR B70 radio relay station.
Condition Indicator nameplate. 
Connection to the transmtter.
Connection to the receiver
All photos in this table by Chris Suslowicz

Credits and References:

1) Chris Suslowicz <chris(at)>

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Aug 24/20